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Design an object-oriented airline management system that handles flight scheduling, multi-class seat inventory (Economy / Business / First), passenger registration, booking with PNR generation, check-in with seat assignment, and flight cancellation / delay handling.
The system models Airports, Aircraft with configurable seat layouts, Flights with per-class pricing and status lifecycle (SCHEDULED → BOARDING → DEPARTED → LANDED / CANCELLED), Bookings (PENDING → CONFIRMED → CHECKED_IN → COMPLETED), and a flight search engine for route-based queries.
Schedule a flight
Create a flight with origin, destination, aircraft, times, and per-class pricing
Search flights
Search available flights by route, date, and seat class
Book a flight
Reserve a seat in a specific class, generate a PNR
Cancel a booking
Cancel a passenger's booking and release the seat
Check-in
Passenger checks in and is assigned a specific seat number
Cancel / delay a flight
Cancel a flight (notify all passengers) or update departure/arrival times
Multi-class seating
Manage separate inventory for Economy, Business, and First class
Passenger itinerary
View all active bookings for a passenger
Frequent flyer miles
Accumulate miles per booking
Before diving into code, clarify the use cases and edge cases. Understanding the problem deeply leads to better class design.
Identify the primary actions users will perform. For a parking lot: park vehicle, exit vehicle, check availability. Each becomes a method.
Who interacts with the system? Customers, admins, automated systems? Each actor type may need different interfaces.
What are the limits? Max vehicles, supported vehicle types, payment methods. Constraints drive your data structures.
What happens on overflow? Concurrent access? Payment failures? Thinking about edge cases reveals hidden complexity.