Airports across the UK including Manchester, Birmingham and all those in London were hit by problems at air traffic control on Tuesday.
The technical issue arose shortly before 2pm and was resolved about three hours later. By that time, hundreds of flights had been cancelled, with knock-on disruption across Britain and at destination airports abroad likely to continue into the evening and possibly Wednesday.
Here we explain what you can expect if you have been affected.
Is your flight delayed or cancelled?
The Civil Aviation Authority (CAA) website explains how long the delay has to be before you are entitled to care and assistance from your airline while you wait. The timeframe differs by flight distance. This assistance should cover food and drink and the ability to make phone calls or send emails, plus accommodation and the necessary transfers if the flight is delayed until the next day.
Many airlines will provide vouchers for you to buy food and drink, and overnight accommodation will typically take the form of a nearby hotel (unless you live nearby, in which case your airline may reimburse your costs for getting to and from home).
Sometimes airline staff are unable to arrange care and assistance for all passengers, in which case you can sort yourself out and claim the cost back later.
But don’t splash the cash – and keep receipts. The CAA says airlines may have guidelines on this, adding: “Airlines are unlikely to consider alcoholic drinks, luxury hotels or luxury meals to be reasonable.”
If your flight has been cancelled and is covered by UK law – that means one departing from an airport in the UK on any airline, or arriving at an airport in the UK on an EU or UK airline, or arriving at an airport in the EU on a UK airline – your airline must offer you the choice of another flight or a refund.
If you select an alternative flight, it is up to you whether you fly as soon as possible or at a later date.
If the delay is more than five hours you can choose not to travel and receive a refund.
I am due to fly imminently – should I still go to the airport?
If you are due to travel on Tuesday evening or Wednesday, check the latest advice from your airport or tour operator, or airline apps and airport social media feeds, for the most up-to-date information.
The air traffic control service provider Nats had advised that it would “take some time” to rectify the problem but at about 5pm it posted on social media that it had “implemented a fix and our flight system is starting to recover”. The knock on impact on flight schedules could take some time to be resolved.
Will I be entitled to compensation from the airline?
If your flight was cancelled or delayed as a result of Tuesday’s issue, you are unlikely to be owed compensation by the airline. This is because the technical issue affecting flights will be considered an extraordinary circumstance and out of the airline’s control.
Causes of disruption classed as outside an airline’s control also include severe weather and security alerts.
Anna-Marie Duthie, a travel insurance expert at the financial ratings company Defaqto, says: “Travel insurance may cover you if you cannot claim costs back from the airline, operator, or credit card but that will all depend on whether your policy includes cover for delay, travel disruption, missed connection or abandonment.”