What is an airline's conditions of carriage, and why should you read it?

The contract between you and the airline — setting out what each side is obliged to do, what happens when things go wrong, and the many things the airline is permitted to do that passengers assume it cannot.

What it covers:

Schedule changes and cancellations, and what the airline owes you.

Denied boarding and the order in which passengers are selected.

Baggage — limits, liability for loss and damage, and excluded items.

Refusal of carriage and the grounds for it.

Conduct on board.

Liability limits, which derive from international convention.

The clauses that surprise people:

Schedules are not guaranteed. Almost every conditions of carriage states that times are not part of the contract and the airline may substitute aircraft, change routes and alter times. This is why a schedule change months ahead is not a breach.

Sequential use of coupons is required. If you miss or skip a segment, the airline may cancel the remainder — which is the clause that defeats hidden city ticketing and also catches people who genuinely intended to skip an outbound leg.

Refusal of carriage grounds are broad, covering conduct, documentation, health and safety.

Baggage liability is capped at limits set by the Montreal Convention, and the cap is frequently well below the value of what people carry — which is why valuables should travel in the cabin and why travel insurance matters.

Time limits for claims are short for baggage — a matter of days for damage — and missing them defeats an otherwise valid claim.

What overrides the contract. Statutory rights take precedence over contractual terms. In the UK and EU, assistance and compensation rules for delays, cancellations and denied boarding apply regardless of what the conditions say, and the airline cannot contract out of them. The Montreal Convention governs international liability for death, injury, delay and baggage.

Where to find it: published on the airline's site, and incorporated into your ticket by reference — meaning you agreed to it whether or not you read it.

Codeshare complicates it: the operating carrier's conditions frequently apply, not the one you booked with.