Design
Airline Management System
Design an airline management system that handles aircraft fleet management, flight scheduling, passenger seat reservation with conflict-free booking, crew assignment, check-in, and boarding pass generation.
This is a Low-Level Design (LLD) problem. New to LLD vs HLD? Start here.
01 - Why interviewers ask this
Airline Management combines several challenging patterns in one problem: concurrent booking with race-condition prevention, multi-step state machines, complex entity relationships (flight → aircraft → seat map → booking → passenger), and constraint-based crew scheduling — making it a reliable signal of mid-to-senior OOP design skills.
02 - Where this system exists in the real world
You interact with this design every day.
Powers global distribution systems (GDS) like Amadeus and Sabre used by all major airlines
Foundation for airline CRS (Computer Reservation Systems) handling millions of bookings daily
Seat map and booking logic is reused in train and bus reservation platforms
Crew scheduling algorithms are used in transport, hospitality, and healthcare workforce management
03 - What you'll master
Solve this once. Know it forever.
Model a multi-entity booking domain with relationship constraints
Implement optimistic locking for concurrent seat reservation
Design a State Machine with real-world business rules guarding transitions
Handle crew assignment with constraint validation (duty hours, certifications)
04 - What you'll design
8 functional · 3 non-functional requirements.
Manage a fleet of aircraft with different seat configurations (Economy, Business, First Class)
7 more requirements inside
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05 - Companies that ask this
You may face this exact question in your next interview.
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