Thousands of British Airways passengers hit by the latest IT glitch are entitled to assistance and compensation, depending on the length of the flight and how long their journey was delayed.

READ MORE: 'Chaos' in Glasgow and other airports after British Airways IT failure

Here are some of the key questions around the rules:

– What rules apply?

European Union law applies to flights either departing from an EU airport or those that are arriving at an EU airport and operated by an EU airline, such as British Airways.

– How long must a flight be delayed before an airline has to provide support?

The length of delay that leads to airlines being required to offer assistance ranges from two hours for short-haul flights to four hours for long-haul flights.

– What care must be offered?

Airlines have to provide vouchers to buy a reasonable amount of food and drink, a means of communication (often by refunding the cost of telephone calls), and accommodation if a passenger is delayed overnight.

Sometimes airlines are unable to arrange care, particularly during major disruption. In this instance, passengers are advised to keep receipts and claim costs back later.

– What if a flight is cancelled?

Airlines have to offer full refunds or re-book passengers on to alternative flights.

– Can passengers claim compensation?

If a journey is delayed by more than three hours due to a factor within the airline’s control – such as technical faults or overbooking – there are fixed levels of compensation that can be claimed.

The amount ranges from 250 euros (£230) for short-haul flights delayed by at least three hours, to 600 euros (£553) for long-haul flights delayed by at least four hours.

– Does this mean travellers are guaranteed a payout every time there is disruption?

Any delays outside an airline’s control, such as bad weather or security alerts, are not liable for compensation.

– Is compensation automatic?

No, disrupted passengers must write a letter of complaint to the airline.