Everywhere: a refund or rebooking, your choice. In the EU/UK: also meals, hotel if overnight, and up to €600 compensation unless the cause was extraordinary. In the US: a cash refund is required for cancellations; compensation is not, though some airlines offer it voluntarily.
United States: if the airline cancels or significantly changes the flight and you don’t travel, you’re owed a full refund to the original payment method — not a voucher — under DOT rules. Meals and hotels depend on the airline’s customer-service plan for controllable delays.
EU and UK (EU261 / UK261): applies to flights departing the EU/UK or arriving on an EU/UK carrier. You get rebooking or refund, care (meals, hotel) while you wait, and compensation of €250–€600 (£220–£520) depending on distance, unless the cause was extraordinary (severe weather, ATC strikes) or you were told 14+ days ahead.
Elsewhere: Canada (APPR), Brazil, Turkey and others have their own schemes; most countries at least require a refund.
Do this: keep receipts, ask for the reason in writing, claim directly with the airline first, and escalate to the regulator or a claims service if refused.
Related questions
What happens if I miss my connecting flight?
On a single ticket, the airline rebooks you on the next available flight at no charge, and may owe meals or a hotel if the delay was its fault. On separate tickets you're on your own — you'll buy a new ticket. Full answer →
Is travel insurance worth it?
For international trips, medical cover alone justifies it — a hospital stay abroad can cost tens of thousands. Trip-cancellation cover is worth it for expensive, non-refundable trips. Check what your credit card already includes before buying. Full answer →
Airline, airport and government rules change without notice. Treat this as a starting point and confirm with the airline or authority for your specific trip. Request a correction if something is out of date.