(Generally, none of these apply if the airline can claim extraordinary circumstances such as weather)
- Flights Originating/Transiting/Ending in the EU:
1. You are entitled to cash compensation for sufficiently long delays (2-4 hours depending on flight duration) 2. You are entitled to cash compensation (for the inconvenience) and reroute (whenever you want) for a cancellation or cash compensation (for the inconvenience) and a ticket refund
If delay is long enough, you are entitled to meals and refreshments, if over-night, to accomodation.
- Flights in the US
AFAIK, you pretty much are only entitled to something if you get denied boarding on an overbooked flight.
However, it's always best to just walk up to an airline agent, putting a smile on your face and explaining the situation. They have nothing against you and only help, but you greatly reduce their inclination to do so by making it their personal fault.