What happens if a flight is delayed?

Regulation (EC) 261/2004 scales the response according to how long the wait lasts and how long the route is. Assistance kicks in at two hours for flights up to 1,500 km, at three hours for those between 1,500 and 3,500 km, and at four hours for longer distances. It includes food and drink appropriate to the waiting time, two phone calls or messages, and accommodation with transfer if departure is rescheduled to another day.

From five hours of delay onward, passengers may withdraw: the airline must refund the ticket price within seven days for the unflown portion, and, if the flight no longer serves the purpose of the trip, also for the portion already flown, with a return flight to the point of departure if applicable.

Lump-sum compensation applies when the passenger reaches their final destination three hours or more late. The airline is exempt if it proves an extraordinary circumstance beyond its control: adverse weather, an air traffic controllers' strike, airspace closure or an order from the authority. Routine maintenance problems, crew shortages or overbooking do not exempt it.

It's worth requesting the cause of the delay in writing and keeping receipts for any expenses if the airline doesn't provide assistance on its own, since these are reimbursable when the amount is reasonable. Outside the European framework the rules change completely; in the United States, for example, there's no mandatory compensation for delays, and in Latin America each national regulator sets its own thresholds. Before filing a claim, it's worth checking which regulation covers the specific route based on the point of departure and the operator's nationality.