Experts have warned that British Airways faces compensation claims that could top £100 million following the bank holiday weekend chaos.
Here are some of the key questions around the claims process:
:: What rules apply?
EU law protects passengers whose flights are delayed or cancelled under the Denied Boarding Regulation.
This applies to flights either departing from an EU airport or those that are both arriving at an EU airport and operated by an EU airline.
:: Does this mean travellers are guaranteed a payout every time there is disruption?
No, airlines only have to provide assistance if the disruption was within its control, such as technical faults or overbooking. Bad weather and strikes do not count.
:: How delayed does a flight have to be to warrant compensation?
Assistance must be provided for short-haul flights delayed by at least two hours, medium-haul flights delayed by three hours and long-haul flights delayed by four hours.
Passengers are entitled to meals, refreshments, phone calls, as well as accommodation if an overnight stay is required.
:: What if a flight is cancelled?
In this instance, airlines have to offer full refunds or re-book passengers onto alternative flights.
:: Can passengers receive cash compensation?
Cancelled short-haul flights can result in 250 euro (£218) payouts, medium-haul 400 euros (£349) and long-haul 600 euros (£524), depending on the timings of alternative flights.
:: Is compensation automatic?
No, disrupted passengers must write a letter of complaint to the airline. They should keep as much evidence as they can, such as boarding cards and receipts to claim expenses.
A template letter can be found on the website of consumer watchdog Which?.
:: What has BA said about compensation?
The airline said in a statement that it will "fully comply with all of the relevant EU compensation regulations" and will be "working as hard as we can to process all payments to customers as quickly as we can".