Airport check-in is a high-pressure environment where clear English can prevent a missed flight, a lost bag, or a serious security issue — and where vague English can do the opposite. The vocabulary in this exercise covers the specific language of passenger check-in: the terms for documents, baggage allowances, seat assignments, boarding procedures, and the careful phrasing that keeps a long queue moving without confusion. Airline check-in staff also deal with the emotional extremes of travel — the panicked late arrival, the family with too much luggage, the passenger whose name doesn't match their ticket — and the English for those situations needs to be as clear under pressure as it is in routine interactions.