Who is left on the ground

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Seven passengers. Six seats. Everyone turned up. Check in closes. Somebody loses. Who, and what do they get?

Line up the ticketed bookings in purchase order. For each, count the free seats and the seats it needs. If it fits, seat it. If not, bump it.

A group of three needs three seats. Two are free. Split them? No. The whole group is bumped as one unit.

The last booking needs two seats. One is free. It gets its fare back: 24,000 cents. Plus compensation, twice the fare per passenger: 48,000. Total 72,000.

Last to buy goes first. That is deterministic, and simple. Real airlines weigh fare class, status and check in time. That is a third strategy that sorts the queue.

Purchase order is deterministic. The same input bumps the same booking. It is also easy to test and to explain to a customer. A policy can replace it without touching the close.

Denied boarding is a designed outcome, with a price.

The full design is in the lecture. Holds, policies, refunds and the close.