# Product Requirements Document: Airlines Management System

## 1. Overview

The Airlines Management System is a streamlined web application designed to manage core airline operations including flight scheduling, aircraft management, passenger bookings, and crew assignments. The system enables airline staff to efficiently manage flights, track aircraft availability, process passenger reservations, and assign crew members to flights. This lightweight solution focuses on essential airline operations without complex authentication layers, providing quick access to critical airline management functions.

## 2. User Roles

### 2.1 Administrator
- Full system access and configuration rights
- Manage aircraft fleet (add, edit, delete aircraft)
- Manage airports and routes
- Manage crew members and their assignments
- View all bookings and generate reports
- Configure system settings and pricing rules

### 2.2 Flight Manager
- Create, update, and cancel flights
- Assign aircraft to flights
- Assign crew members to flights
- View flight schedules and availability
- Manage flight status (scheduled, boarding, departed, arrived, cancelled, delayed)
- View passenger manifests for flights

### 2.3 Booking Agent
- Search available flights
- Create and manage passenger bookings
- Process ticket reservations
- Cancel and modify bookings
- View booking history
- Generate booking confirmations

### 2.4 Crew Member (View-Only)
- View assigned flights
- View flight schedules
- View crew assignments
- Access flight details and routes

## 3. Core Entities

### 3.1 Aircraft
Represents individual airplanes in the fleet with registration details, model information, and seating capacity.

### 3.2 Airport
Represents airports with code, name, city, country, and timezone information.

### 3.3 Route
Represents a flight path between two airports with distance and estimated duration.

### 3.4 Flight
Represents a scheduled flight instance with departure/arrival times, assigned aircraft, route, pricing, and status.

### 3.5 Crew Member
Represents airline staff (pilots, co-pilots, flight attendants) with personal details, role, and certification information.

### 3.6 Flight Crew Assignment
Represents the assignment of crew members to specific flights with their role on that flight.

### 3.7 Passenger
Represents individuals who book flights with personal and contact information.

### 3.8 Booking
Represents a flight reservation made by a passenger with booking status, seat assignment, and payment information.

### 3.9 Seat
Represents individual seats on an aircraft with class type and availability status.

### 3.10 Fare Class
Represents pricing tiers (Economy, Business, First Class) with associated rules and pricing multipliers.

## 4. Entity Relationships

### 4.1 Aircraft Relationships
- **Aircraft → Seat**: One-to-Many (one aircraft has many seats)
- **Aircraft → Flight**: One-to-Many (one aircraft can be assigned to many flights over time)

### 4.2 Airport Relationships
- **Airport → Route (Origin)**: One-to-Many (one airport can be origin for many routes)
- **Airport → Route (Destination)**: One-to-Many (one airport can be destination for many routes)

### 4.3 Route Relationships
- **Route → Flight**: One-to-Many (one route can have many scheduled flights)
- **Route → Airport (Origin)**: Many-to-One (many routes can share same origin airport)
- **Route → Airport (Destination)**: Many-to-One (many routes can share same destination airport)

### 4.4 Flight Relationships
- **Flight → Route**: Many-to-One (many flights belong to one route)
- **Flight → Aircraft**: Many-to-One (many flights can use same aircraft)
- **Flight → Booking**: One-to-Many (one flight has many bookings)
- **Flight → Flight Crew Assignment**: One-to-Many (one flight has many crew assignments)

### 4.5 Crew Member Relationships
- **Crew Member → Flight Crew Assignment**: One-to-Many (one crew member has many flight assignments)

### 4.6 Flight Crew Assignment Relationships
- **Flight Crew Assignment → Flight**: Many-to-One (many assignments belong to one flight)
- **Flight Crew Assignment → Crew Member**: Many-to-One (many assignments belong to one crew member)

### 4.7 Passenger Relationships
- **Passenger → Booking**: One-to-Many (one passenger can have many bookings)

### 4.8 Booking Relationships
- **Booking → Passenger**: Many-to-One (many bookings belong to one passenger)
- **Booking → Flight**: Many-to-One (many bookings belong to one flight)
- **Booking → Seat**: Many-to-One (many bookings can reference one seat)
- **Booking → Fare Class**: Many-to-One (many bookings belong to one fare class)

### 4.9 Seat Relationships
- **Seat → Aircraft**: Many-to-One (many seats belong to one aircraft)
- **Seat → Booking**: One-to-Many (one seat can be booked across different flights)

### 4.10 Fare Class Relationships
- **Fare Class → Booking**: One-to-Many (one fare class applies to many bookings)

## 5. Key Workflows

### 5.1 Flight Creation Workflow
1. Flight Manager selects a route from available routes
2. System displays route details (origin, destination, distance, duration)
3. Flight Manager enters flight number and scheduled departure date/time
4. System calculates estimated arrival time based on route duration
5. Flight Manager selects available aircraft from fleet
6. System validates aircraft availability for the time slot
7. Flight Manager sets base fare price
8. System creates flight with status "Scheduled"
9. System generates available seats based on aircraft configuration
10. Flight is now available for booking

### 5.2 Crew Assignment Workflow
1. Flight Manager views scheduled flight details
2. System displays required crew positions (Captain, First Officer, Flight Attendants)
3. Flight Manager searches available crew members by role and date
4. System filters crew members not assigned to conflicting flights
5. Flight Manager selects crew member and assigns role for the flight
6. System validates crew member certifications and availability
7. System creates flight crew assignment record
8. Crew member can now view assignment in their schedule
9. Process repeats until all required positions are filled

### 5.3 Booking Creation Workflow
1. Booking Agent enters search criteria (origin, destination, date)
2. System displays available flights matching criteria
3. Booking Agent selects desired flight
4. System displays available seats by fare class with pricing
5. Booking Agent enters passenger information (name, email, phone, passport)
6. System checks if passenger exists; creates new passenger record if needed
7. Booking Agent selects seat and fare class
8. System calculates total fare based on base price and fare class multiplier
9. Booking Agent confirms booking details
10. System creates booking with status "Confirmed"
11. System marks seat as occupied for that flight
12. System generates booking reference number
13. Booking confirmation is displayed with all details

### 5.4 Booking Modification Workflow
1. Booking Agent searches for booking by reference number or passenger name
2. System displays booking details and current status
3. Booking Agent selects modification type (change seat, change flight, cancel)
4. **If changing seat:**
   - System displays available seats on same flight
   - Agent selects new seat
   - System updates booking and seat availability
5. **If changing flight:**
   - System displays alternative flights on same route
   - Agent selects new flight and seat
   - System validates availability and updates booking
   - System recalculates fare if price difference exists
6. **If cancelling:**
   - Agent confirms cancellation
   - System updates booking status to "Cancelled"
   - System releases seat for rebooking
7. System generates updated confirmation

### 5.5 Flight Status Management Workflow
1. Flight Manager views list of scheduled flights
2. Flight Manager selects flight to update
3. System displays current flight status and details
4. Flight Manager updates status based on operation:
   - **Boarding**: Flight is ready for passenger boarding
   - **Departed**: Flight has taken off
   - **Delayed**: Flight is delayed (enter new departure time)
   - **Arrived**: Flight has landed at destination
   - **Cancelled**: Flight is cancelled (system notifies all bookings)
5. System timestamps the status change
6. If status is "Cancelled", system updates all associated bookings to "Cancelled"
7. System logs status history for reporting

### 5.6 Aircraft Maintenance Scheduling Workflow
1. Administrator views aircraft fleet list
2. Administrator selects aircraft for maintenance
3. Administrator enters maintenance start and end dates
4. System checks for flights assigned to aircraft during maintenance period
5. System displays conflicts if any flights are scheduled
6. Administrator either:
   - Cancels conflicting flights, or
   - Reassigns conflicting flights to different aircraft
7. System marks aircraft as "Under Maintenance" for the period
8. Aircraft becomes unavailable for flight assignments during maintenance

## 6. Features & Requirements

### 6.1 Aircraft Management Module

#### 6.1.1 Aircraft Registration
- **FR-AM-001**: System shall allow administrators to add new aircraft with registration number, model, manufacturer, and total capacity
- **FR-AM-002**: System shall validate unique aircraft registration numbers
- **FR-AM-003**: System shall allow administrators to edit aircraft details
- **FR-AM-004**: System shall allow administrators to deactivate aircraft (soft delete)
- **FR-AM-005**: System shall display aircraft status (Active, Under Maintenance, Retired)

#### 6.1.2 Aircraft Seat Configuration
- **FR-AM-006**: System shall allow administrators to configure seats for each aircraft
- **FR-AM-007**: System shall support seat numbering (e.g., 1A, 1B, 2A, etc.)
- **FR-AM-008**: System shall assign seat class (Economy, Business, First Class) to each seat
- **FR-AM-009**: System shall validate total seats match aircraft capacity
- **FR-AM-010**: System shall allow bulk seat generation based on configuration template

#### 6.1.3 Aircraft Availability
- **FR-AM-011**: System shall display aircraft availability calendar
- **FR-AM-012**: System shall show all flights assigned to an aircraft
- **FR-AM-013**: System shall prevent double-booking of aircraft for overlapping flight times
- **FR-AM-014**: System shall calculate turnaround time between flights (minimum 2 hours)

### 6.2 Airport & Route Management Module

#### 6.2.1 Airport Management
- **FR-AR-001**: System shall allow administrators to add airports with IATA code, name, city, country, and timezone
- **FR-AR-002**: System shall validate unique IATA codes (3-letter format)
- **FR-AR-003**: System shall allow administrators to edit airport information
- **FR-AR-004**: System shall display list of all airports with search and filter capabilities
- **FR-AR-005**: System shall allow administrators to deactivate airports

#### 6.2.2 Route Management
- **FR-AR-006**: System shall allow administrators to create routes between two airports
- **FR-AR-007**: System shall prevent creation of routes with same origin and destination
- **FR-AR-008**: System shall store route distance in kilometers
- **FR-AR-009**: System shall store estimated flight duration in minutes
- **FR-AR-010**: System shall allow administrators to edit route details
- **FR-AR-011**: System shall display all routes with origin and destination information
- **FR-AR-012**: System shall allow administrators to deactivate routes
- **FR-AR-013**: System shall support bidirectional routes (A→B and B→A as separate routes)

### 6.3 Flight Management Module

#### 6.3.1 Flight Scheduling
- **FR-FM-001**: System shall allow flight managers to create flights with flight number, route, departure date/time, and aircraft
- **FR-FM-002**: System shall auto-calculate arrival time based on departure time and route duration
- **FR-FM-003**: System shall validate aircraft availability before flight creation
- **FR-FM-004**: System shall validate flight number uniqueness for the same date
- **FR-FM-005**: System shall allow flight managers to set base fare price
- **FR-FM-006**: System shall allow flight managers to edit flight details before departure
- **FR-FM-007**: System shall prevent editing of departed or arrived flights
- **FR-FM-008**: System shall allow flight managers to cancel flights

#### 6.3.2 Flight Status Management
- **FR-FM-009**: System shall support flight statuses: Scheduled, Boarding, Departed, Arrived, Delayed, Cancelled
- **FR-FM-010**: System shall allow flight managers to update flight status
- **FR-FM-011**: System shall timestamp all status changes
- **FR-FM-012**: System shall maintain status change history
- **FR-FM-013**: System shall allow flight managers to update departure/arrival times for delayed flights
- **FR-FM-014**: System shall automatically cancel all bookings when flight is cancelled

#### 6.3.3 Flight Search & Display
- **FR-FM-015**: System shall allow users to search flights by origin, destination, and date
- **FR-FM-016**: System shall display flight results with flight number, departure/arrival times, duration, aircraft, and available seats
- **FR-FM-017**: System shall filter flights by status
- **FR-FM-018**: System shall display seat availability by fare class
- **FR-FM-019**: System shall allow sorting flights by departure time, price, or duration
- **FR-FM-020**: System shall display flight details including route, aircraft, and crew assignments

### 6.4 Crew Management Module

#### 6.4.1 Crew Member Management
- **FR-CM-001**: System shall allow administrators to add crew members with name, employee ID, role, email, phone, and certification details
- **FR-CM-002**: System shall support crew roles: Captain, First Officer, Flight Attendant, Purser
- **FR-CM-003**: System shall validate unique employee IDs
- **FR-CM-004**: System shall allow administrators to edit crew member information
- **FR-CM-005**: System shall allow administrators to deactivate crew members
- **FR-CM-006**: System shall store crew member certification numbers and expiry dates
- **FR-CM-007**: System shall display crew member status (Active, On Leave, Inactive)

#### 6.4.2 Crew Assignment
- **FR-CM-008**: System shall allow flight managers to assign crew members to flights
- **FR-CM-009**: System shall specify crew role for each flight assignment (e.g., Captain, Flight Attendant)
- **FR-CM-010**: System shall validate crew member availability (no overlapping flight assignments)
- **FR-CM-011**: System shall validate crew member certifications are current
- **FR-CM-012**: System shall allow flight managers to remove crew assignments
- **FR-CM-013**: System shall display all crew assignments for a flight
- **FR-CM-014**: System shall display flight schedule for each crew member
- **FR-CM-015**: System shall enforce minimum crew requirements per flight (1 Captain, 1 First Officer, minimum 2 Flight Attendants)

#### 6.4.3 Crew Schedule View
- **FR-CM-016**: System shall allow crew members to view their assigned flights
- **FR-CM-017**: System shall display crew schedule in calendar format
- **FR-CM-018**: System shall show flight details for each assignment
- **FR-CM-019**: System shall allow crew members to filter schedule by date range

### 6.5 Passenger & Booking Management Module

#### 6.5.1 Passenger Management
- **FR-PB-001**: System shall allow booking agents to create passenger records with first name, last name, email, phone, passport number, and date of birth
- **FR-PB-002**: System shall validate email format
- **FR-PB-003**: System shall validate passport number format
- **FR-PB-004**: System shall allow booking agents to search passengers by name, email, or passport
- **FR-PB-005**: System shall allow booking agents to edit passenger information
- **FR-PB-006**: System shall display booking history for each passenger

#### 6.5.2 Booking Creation
- **FR-PB-007**: System shall allow booking agents to create bookings for passengers on available flights
- **FR-PB-008**: System shall generate unique booking reference numbers (alphanumeric, 6 characters)
- **FR-PB-009**: System shall allow booking agents to select seat and fare class
- **FR-PB-010**: System shall calculate total fare based on base price and fare class multiplier
- **FR-PB-011**: System shall validate seat availability before booking confirmation
- **FR-PB-012**: System shall mark seat as occupied after booking confirmation
- **FR-PB-013**: System shall set booking status to "Confirmed" upon creation
- **FR-PB-014**: System shall timestamp booking creation
- **FR-PB-015**: System shall allow booking multiple passengers on same flight in single transaction

#### 6.5.3 Booking Management
- **FR-PB-016**: System shall allow booking agents to search bookings by reference number, passenger name, or flight number
- **FR-PB-017**: System shall display booking details including passenger, flight, seat, fare class, and total price
- **FR-PB-018**: System shall allow booking agents to modify seat assignment
- **FR-PB-019**: System shall allow booking agents to change flight (subject to availability)
- **FR-PB-020**: System shall allow booking agents to cancel bookings
- **FR-PB-021**: System shall update booking status to "Cancelled" upon cancellation
- **FR-PB-022**: System shall release seat when booking is cancelled
- **FR-PB-023**: System shall maintain booking modification history
- **FR-PB-024**: System shall support booking statuses: Confirmed, Cancelled, Checked-In, Completed

#### 6.5.4 Booking Confirmation
- **FR-PB-025**: System shall display booking confirmation with all details after successful booking
- **FR-PB-026**: System shall show booking reference number prominently
- **FR-PB-027**: System shall display passenger details, flight information, seat assignment, and total fare
- **FR-PB-028**: System shall allow printing or downloading booking confirmation

### 6.6 Fare Class Management Module

#### 6.6.1 Fare Class Configuration
- **FR-FC-001**: System shall support fare classes: Economy, Business, First Class
- **FR-FC-002**: System shall allow administrators to configure fare class multipliers (e.g., Economy: 1.0x, Business: 2.5x, First: 4.0x)
- **FR-FC-003**: System shall allow administrators to set fare class descriptions and benefits
- **FR-FC-004**: System shall allow administrators to edit fare class details
- **FR-FC-005**: System shall apply fare class multiplier to flight base price for final ticket price

#### 6.6.2 Fare Calculation
- **FR-FC-006**: System shall calculate ticket price as: Base Fare × Fare Class Multiplier
- **FR-FC-007**: System shall display price breakdown showing base fare and fare class
- **FR-FC-008**: System shall round final prices to 2 decimal places
- **FR-FC-009**: System shall display prices in configured currency (default: USD)

### 6.7 Reporting & Analytics Module

#### 6.7.1 Flight Reports
- **FR-RA-001**: System shall generate flight schedule reports by date range
- **FR-RA-002**: System shall generate passenger manifest reports per flight
- **FR-RA-003**: System shall generate flight occupancy reports showing booked vs. available seats
- **FR-RA-004**: System shall generate flight status reports

#### 6.7.2 Booking Reports
- **FR-RA-005**: System shall generate booking reports by date range
- **FR-RA-006**: System shall generate revenue reports by flight, route, or date range
- **FR-RA-007**: System shall generate cancellation reports
- **FR-RA-008**: System shall display booking statistics (total bookings, cancellations, revenue)

#### 6.7.3 Crew Reports
- **FR-RA-009**: System shall generate crew utilization reports
- **FR-RA-010**: System shall generate crew schedule reports by crew member or date range
- **FR-RA-011**: System shall display crew assignment statistics

#### 6.7.4 Aircraft Reports
- **FR-RA-012**: System shall generate aircraft utilization reports
- **FR-RA-013**: System shall generate aircraft maintenance schedule reports
- **FR-RA-014**: System shall display aircraft availability statistics

### 6.8 Dashboard Module

#### 6.8.1 Overview Dashboard
- **FR-DB-001**: System shall display dashboard with key metrics upon access
- **FR-DB-002**: System shall show total flights scheduled for current day
- **FR-DB-003**: System shall show total bookings for current day
- **FR-DB-004**: System shall show total revenue for current month
- **FR-DB-005**: System shall show fleet status (active aircraft, under maintenance)
- **FR-DB-006**: System shall show upcoming flights (next 24 hours)
- **FR-DB-007**: System shall show recent bookings
- **FR-DB-008**: System shall display alerts for delayed or cancelled flights
- **FR-DB-009**: System shall show crew members on duty today

## 7. Business Rules

### 7.1 Aircraft Rules
- **BR-AC-001**: Aircraft registration number must be unique across the system
- **BR-AC-002**: Aircraft cannot be deleted if it has future flight assignments
- **BR-AC-003**: Aircraft must have at least one seat configured before being assigned to flights
- **BR-AC-004**: Aircraft under maintenance cannot be assigned to new flights
- **BR-AC-005**: Aircraft must have minimum 2-hour turnaround time between flights
- **BR-AC-006**: Total configured seats must not exceed aircraft capacity

### 7.2 Airport & Route Rules
- **BR-AR-001**: Airport IATA code must be exactly 3 uppercase letters
- **BR-AR-002**: Airport IATA code must be unique across the system
- **BR-AR-003**: Route origin and destination airports must be different
- **BR-AR-004**: Route distance must be greater than 0 kilometers
- **BR-AR-005**: Route duration must be greater than 0 minutes
- **BR-AR-006**: Airports cannot be deleted if they are part of active routes
- **BR-AR-007**: Routes cannot be deleted if they have future scheduled flights

### 7.3 Flight Rules
- **BR-FL-001**: Flight number must be unique for the same departure date
- **BR-FL-002**: Flight departure time must be in the future at time of creation
- **BR-FL-003**: Flight arrival time must be after departure time
- **BR-FL-004**: Aircraft must be available (not assigned to overlapping flights) for the flight duration plus turnaround time
- **BR-FL-005**: Base fare must be greater than 0
- **BR-FL-006**: Flights cannot be edited or deleted after status is "Departed" or "Arrived"
- **BR-FL-007**: Cancelled flights cannot be reactivated
- **BR-FL-008**: Flight status transitions must follow logical sequence (Scheduled → Boarding → Departed → Arrived)
- **BR-FL-009**: Delayed flights must have updated departure time in the future
- **BR-FL-010**: Flights must have assigned aircraft before accepting bookings

### 7.4 Crew Rules
- **BR-CR-001**: Crew member employee ID must be unique across the system
- **BR-CR-002**: Crew member cannot be assigned to overlapping flights (considering flight duration + travel time)
- **BR-CR-003**: Crew member certifications must be valid (not expired) at time of flight
- **BR-CR-004**: Each flight must have at least 1 Captain assigned
- **BR-CR-005**: Each flight must have at least 1 First Officer assigned
- **BR-CR-006**: Each flight must have minimum 2 Flight Attendants assigned
- **BR-CR-007**: Maximum 1 Captain and 1 First Officer per flight
- **BR-CR-008**: Crew members cannot be deleted if they have future flight assignments
- **BR-CR-009**: Crew member must have minimum 12-hour rest period between flight assignments

### 7.5 Passenger & Booking Rules
- **BR-PB-001**: Passenger email must be in valid email format
- **BR-PB-002**: Passenger passport number must be alphanumeric and 6-12 characters
- **BR-PB-003**: Passenger date of birth must indicate passenger is at least 0 years old (infants allowed)
- **BR-PB-004**: Booking reference number must be unique across the system
- **BR-PB-005**: Seat can only be booked once per flight
- **BR-PB-006**: Bookings can only be made for flights with status "Scheduled"
- **BR-PB-007**: Bookings cannot be made for flights in the past
- **BR-PB-008**: Bookings cannot be made if flight is fully booked
- **BR-PB-009**: Cancelled bookings cannot be reactivated (must create new booking)
- **BR-PB-010**: Seat changes are only allowed to available seats on the same flight
- **BR-PB-011**: Flight changes are only allowed to flights on the same route with available seats
- **BR-PB-012**: Bookings are automatically cancelled when flight is cancelled
- **BR-PB-013**: Passenger must be at least 18 years old to book without guardian information
- **BR-PB-014**: Total bookings for a flight cannot exceed aircraft seat capacity

### 7.6 Fare Class Rules
- **BR-FC-001**: Fare class multiplier must be greater than 0
- **BR-FC-002**: Economy fare class multiplier must be 1.0 (base price)
- **BR-FC-003**: Business and First Class multipliers must be greater than Economy
- **BR-FC-004**: Fare classes cannot be deleted if they have existing bookings
- **BR-FC-005**: Final ticket price must be rounded to 2 decimal places
- **BR-FC-006**: Seat assignment must match available fare class seats on aircraft

### 7.7 System-Wide Rules
- **BR-SY-001**: All dates and times must be stored in UTC and converted to local timezone for display
- **BR-SY-002**: All monetary values must be stored with 2 decimal precision
- **BR-SY-003**: Soft delete must be used for all entities (mark as inactive rather than physical deletion)
- **BR-SY-004**: All user actions must be timestamped with creation and modification dates
- **BR-SY-005**: System must prevent orphaned records (e.g., bookings without passengers or flights)

## 8. Non-Functional Requirements

### 8.1 Performance Requirements

#### 8.1.1 Response Time
- **NFR-PF-001**: Page load time shall not exceed 2 seconds under normal load
- **NFR-PF-002**: Flight search results shall be returned within 1 second
- **NFR-PF-003**: Booking creation shall complete within 3 seconds
- **NFR-PF-004**: Report generation shall complete within 10 seconds for standard date ranges (up to 1 month)
- **NFR-PF-005**: Dashboard shall load within 2 seconds

#### 8.1.2 Throughput
- **NFR-PF-006**: System shall support at least 100 concurrent users
- **NFR-PF-007**: System shall handle at least 50 booking transactions per minute
- **NFR-PF-008**: System shall support at least 200 flight searches per minute

#### 8.1.3 Database Performance
- **NFR-PF-009**: Database queries shall be optimized with appropriate indexes
- **NFR-PF-010**: Complex queries (reports) shall use database views or materialized views where appropriate
- **NFR-PF-011**: Database connection pooling shall be implemented for efficient resource usage

### 8.2 Scalability Requirements

- **NFR-SC-001**: System architecture shall support horizontal scaling for increased load
- **NFR-SC-002**: Database shall support at least 1 million booking records without performance degradation
- **NFR-SC-003**: System shall support at least 10,000 flights per year
- **NFR-SC-004**: System shall support at least 100 aircraft in the fleet
- **NFR-SC-005**: System shall support at least 500 crew members
- **NFR-SC-006**: System shall support at least 100,000 passenger records

### 8.3 Security Requirements

#### 8.3.1 Data Security
- **NFR-SE-001**: All sensitive data (passport numbers, personal information) shall be encrypted at rest
- **NFR-SE-002**: All data transmission shall use HTTPS/TLS encryption
- **NFR-SE-003**: Database credentials shall be stored securely using environment variables or secret management systems
- **NFR-SE-004**: SQL injection prevention shall be implemented through parameterized queries
- **NFR-SE-005**: Cross-Site Scripting (XSS) protection shall be implemented on all input fields

#### 8.3.2 Access Control
- **NFR-SE-006**: Role-based access control shall be enforced for all features (even without login page, roles are assigned)
- **NFR-SE-007**: Users shall only access features permitted for their role
- **NFR-SE-008**: Sensitive operations (delete, cancel) shall require confirmation
- **NFR-SE-009**: API endpoints shall validate user roles before processing requests

#### 8.3.3 Data Privacy
- **NFR-SE-010**: System shall comply with data privacy regulations (GDPR considerations)
- **NFR-SE-011**: Passenger personal information shall only be accessible to authorized roles
- **NFR-SE-012**: System shall support data anonymization for reporting purposes
- **NFR-SE-013**: Audit logs shall track all data modifications with user and timestamp

### 8.4 Reliability & Availability Requirements

- **NFR-RA-001**: System shall have 99% uptime during business hours
- **NFR-RA-002**: System shall implement graceful error handling with user-friendly error messages
- **NFR-RA-003**: System shall implement database transaction management to ensure data consistency
- **NFR-RA-004**: System shall implement automatic retry logic for transient failures
- **NFR-RA-005**: System shall maintain data integrity during concurrent operations (e.g., multiple agents booking same seat)
- **NFR-RA-006**: System shall implement database backups daily
- **NFR-RA-007**: System shall support point-in-time recovery for critical data loss scenarios

### 8.5 Usability Requirements

- **NFR-US-001**: User interface shall be intuitive and require minimal training
- **NFR-US-002**: System shall provide clear feedback for all user actions (success, error, warnings)
- **NFR-US-003**: Forms shall include inline validation with clear error messages
- **NFR-US-004**: System shall be responsive and work on desktop, tablet, and mobile devices
- **NFR-US-005**: System shall use consistent UI patterns and components throughout
- **NFR-US-006**: System shall provide helpful tooltips and guidance for complex operations
- **NFR-US-007**: System shall support keyboard navigation for accessibility
- **NFR-US-008**: System shall use clear, consistent terminology throughout the interface

### 8.6 Maintainability Requirements

- **NFR-MA-001**: Code shall follow consistent coding standards and style guides
- **NFR-MA-002**: System shall be modular with clear separation of concerns
- **NFR-MA-003**: API shall be RESTful with clear, consistent endpoint naming
- **NFR-MA-004**: Database schema shall be version-controlled with migration scripts
- **NFR-MA-005**: System shall include comprehensive error logging for debugging
- **NFR-MA-006**: Code shall include inline comments for complex business logic
- **NFR-MA-007**: System shall include API documentation (e.g., Swagger/OpenAPI)

### 8.7 Compatibility Requirements

- **NFR-CO-001**: System shall support modern web browsers (Chrome, Firefox, Safari, Edge - latest 2 versions)
- **NFR-CO-002**: System shall be compatible with mobile browsers (iOS Safari, Chrome Mobile)
- **NFR-CO-003**: Backend shall be database-agnostic where possible (support PostgreSQL, MySQL)
- **NFR-CO-004**: System shall use standard web technologies (HTML5, CSS3, JavaScript)
- **NFR-CO-005**: API shall follow REST standards for easy integration

### 8.8 Data Integrity Requirements

- **NFR-DI-001**: System shall enforce referential integrity through foreign key constraints
- **NFR-DI-002**: System shall validate all input data before database insertion
- **NFR-DI-003**: System shall use database transactions for multi-step operations
- **NFR-DI-004**: System shall implement optimistic locking for concurrent updates
- **NFR-DI-005**: System shall maintain audit trails for critical data changes
- **NFR-DI-006**: System shall prevent orphaned records through cascade rules or validation

### 8.9 Localization Requirements

- **NFR-LO-001**: System shall support date/time display in multiple formats
- **NFR-LO-002**: System shall support timezone conversion for international flights
- **NFR-LO-003**: System shall support currency display configuration
- **NFR-LO-004**: System shall use UTC for all internal date/time storage
- **NFR-LO-005**: System shall display local times for departure/arrival based on airport timezone

### 8.10 Monitoring & Logging Requirements

- **NFR-MO-001**: System shall log all errors with stack traces and context
- **NFR-MO-002**: System shall log all critical operations (bookings, cancellations, flight changes)
- **NFR-MO-003**: System shall implement application performance monitoring
- **NFR-MO-004**: System shall track key metrics (bookings per day, revenue, occupancy rates)
- **NFR-MO-005**: System shall provide health check endpoints for monitoring
- **NFR-MO-006**: Logs shall be structured and searchable
- **NFR-MO-007**: System shall retain logs for at least 90 days

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**Document Version**: 1.0  
**Last Updated**: 2025-01-10  
**Domain**: Travels and Tours  
**Domain URL**: https://harsh.dev.dalfin.ai