Flights have been delayed and cancelled at European airports after a cyber attack targeted a service provider for check-in and boarding systems on Saturday (20 September).

Brussels Airport said the attack had rendered automated systems inoperable, allowing only manual check-in and boarding procedures, while London Heathrow and Berlin Airport also said the attack was disrupting flights.

Travellers may be entitled to care while they wait - but not, as this was beyond the control of airlines, compensation. But your rights depend on where your flight begins and the airline involved.

For all flights from the UK and EU airports (as well as those in the wider EEA), European air passengers' rights rules prevail. These were introduced in 2006 and are known as EC261. After Brexit, the UK copied and pasted the same regulations into British law as UK261.

The rules were devised to require airlines to do the right thing for their passengers. They specify the care and compensation you can expect when your plane is cancelled or heavily delayed.

These rules also apply for flights on EU and British airlines departing from outside the European Union and the UK.

A cancellation, or even a delay of hours rather than minutes, could trigger the obligation for an airline to provide a hotel room and meals as appropriate. If the airline is to blame, it will also owe hundreds of pounds in cash.

Conversely, when flying on a non-EU/UK carrier from outside Europe, you may just have to put a dismal aviation episode down to an expensive experience, and see if your travel insurer can help.

These are the key questions and answers.

For delays of under two hours, you have no rights (unless a short delay in the UK triggers a missed connection and much later arrival at your final ticketed destination - see below).

For longer delays, the airline should provide refreshments as appropriate after a specified length of time. This applies regardless of the cause of the delay.

The time at which the duty of care kicks in depends on the distance you are flying:

Note that if the airline believes providing the care would further delay the flight, it need not deliver.

If the delay extends overnight, the airline is obliged to find and pay for a hotel room. In practice, carriers often say, "too difficult", and invite the passenger to book their own and reclaim later.

While this practice does not comply fully with the rules, aviation authorities tend to turn a blind eye to it.

If you are booked on a UK or EU airline, you have full rights as above. On any other airline, you have none - though in practice a reputable airline will provide meals and accommodation as appropriate.

Some travel insurance policies will help meet expenses that cannot be claimed back elsewhere, and may pay a modest amount of flight delay compensation.

If your flight is cancelled, and you decide not to travel, you should get money back within a week. Some airlines may offer a voucher instead. If there is a benefit in taking a voucher - say an "uplift" in value of 25 per cent - and you know you will be using the same airline within a year, that might be a good decision. But easyJet, Britain's biggest budget airline, does not offer any benefits - it insists on cash.

If you are flying from a UK/EU airport or on a British/ European airline and have your flight cancelled - or are delayed in arrival by at least three hours - the presumption is that you are owed hundreds of pounds in compensation.

The payment depends on distance:

The only way the airline can avoid paying out is by demonstrating "extraordinary circumstances" were responsible.

The rules provide only a partial answer: "political instability, meteorological conditions incompatible with the operation of the flight concerned, security risks, unexpected flight safety shortcomings and strikes".

Court cases have gradually refined the concept of "extraordinary circumstances" to exclude technical problems. In other words: if a mechanical failure caused the delay, you are due compensation. A judge ruled such issues are "inherent in the normal exercise of the activity of the air carrier".

Official strikes by the airline's own staff are regarded as within the carrier's control, but oddly "wildcat" walkouts not sanctioned by a trade union are not.

Crew sickness is a grey area, with no legal certainty.

Ryanair says: "Only a small number of claims will be eligible for compensation. Most delays/cancellations are out of Ryanair's control."

Each airline should enable you to fill out an online form, but these are sometimes difficult to track down. The pages for three leading airlines are here:

Compensation must be paid by bank transfer (or cheque), except if the airline obtains the prior signed agreement of the passenger to pay with vouchers for future travel.

For example, an airline might offer a 30 per cent uplift if you accept vouchers that are valid for a year - so a choice between £350 in cash or £455-worth of flights.

One course of action is alternative dispute resolution, but The Independent has serious reservations about some of the decisions of these arbiters.

Writing a Letter Before Action - warning that you will go to Money Claim Online if you do not get a positive response within two weeks - is worth trying, so long as you follow through. For a £350 claim the fee is £50, which is refunded if you win.

Since Brexit UK citizens no longer have access to the European Small Claims Procedure, so if you are chasing compensation on a flight originating in the EU it might be easiest to go through a claims handler. One such firm is AirHelp, but be warned that the company will keep between 35 and 50 per cent of any payout (the higher amount if court action is involved).

If you arrive at your final ticketed destination three hours or more late, you are still in line for compensation - as long as the cause was down to the airline.

For example, in 2018, I flew on British Airways from Heathrow to Moscow for an onward connection to Volgograd on the Russian airline S7. The plane was an hour late leaving London because of overrunning engineering work. I missed the connection in Moscow and arrived five hours behind schedule at Volgograd.

BA paid delay compensation without a fuss; the issue of meals was easily solved because S7 sent me to the business lounge to wait.

It is notable that in the CAA delay figures for 2023, almost all the airlines that are largely feeding "hub" airports did better than the average: Air France, Emirates, KLM, Lufthansa and Qatar Airways all outplayed easyJet and Ryanair in getting planes away on time.

They have a strong incentive for punctuality, with connections sometimes less than an hour and the penalty for messing up so high.

Turkish Airlines is unique among the big network carriers with an average delay of 29 minutes, which must wreck a significant number of transfers.

Airports' cyber attack: What rights do you have over cancelled flights?