Source: Sky News
Disruption to air travel continued into Tuesday after the UK's air traffic control systems suffered a "technical fault" on Monday morning.
The issue was "identified and remedied" around 3.30pm on Monday - but that doesn't mean a swift end to disruption.
NATS, the National Air Traffic Controllers said it had "identified and remedied" the technical issue affecting its flight planning system.
"We are now working closely with airlines and airports to manage the flights affected as efficiently as possible," it said in a statement.
"Our engineers will be carefully monitoring the system's performance as we return to normal operations."
The fault had affected the system's ability to automatically process flight plans, which means they had to be inputted manually by staff.
As this cannot be done at the same speed, traffic flow restrictions had to be enforced.
Earlier on Monday NATS said it had been hit by a "technical issue" but said the UK's airspace was "not closed".
They reduced the number of aircraft that could take off and land at a given time to manage flow.
What's happening to flights?
For passengers, the changes to traffic flow restrictions means delays and possible cancellations.
Flights were being held on the tarmac or diverted to airports in Ireland or mainland Europe, travel journalist Simon Calder told Sky News.
"There are hundreds of planes up in the sky heading to the UK," he said - meaning hundreds of thousands of passengers could be affected.
The August bank holiday is one of the busiest days of the year for air travel.
Mr Calder said some flights would be able to land as air traffic controllers switched from digital to "much more analogue" systems, but the rate would be much slower.
How long could the disruption last?
Aviation analysts fear yesterday's disruption could have knock-on effects that last well into this week - with planes in the wrong places, and a backlog of passengers to get through.
National Air Traffic Services operations director Juliet Kennedy has warned "it will take some time for flights to return to normal".
Which airports are reporting disruption?
Airlines have released statements about how services will be impacted on Tuesday.
Heathrow Airport has said its services will "remain significantly disrupted". Britain's busiest airport urged passengers to contact their airline before travelling to the airport.
"The issue has been resolved, however schedules remain significantly disrupted," it said. "If you are travelling on 29th August, please ensure you contact your airline before travelling to the airport."
London Gatwick said it plans to operate a normal schedule today following the disruption. However, passengers have been advised to check the status of their flight with their airline before travelling to the airport.
London Stansted also said it planned to run a normal flight schedule on Tuesday, but added "our terminal may be busier than anticipated".
Luton Airport said "flights may be subject to delay or cancellation".
What are airlines saying?
Scottish airline Loganair, one of the first to report disruption, said there was a "network-wide failure of UK air traffic control computer systems" on Monday morning.
"Although we are hopeful of being able to operate most intra-Scotland flights on the basis of local coordination and with a minimum of disruption, north-south and international flights may be subject to delays," the airline posted on X, formerly known as Twitter.
Major UK airlines such as Tui and BA warned of "significant delays" for passengers amid changes to schedules.
EasyJet said: "We are providing customers on cancelled flights with the option to transfer their flight free of charge or receive a refund."
What should I do if I'm travelling?
If you're due to fly in or out of the UK, check the status of your flight with your airline - this is what each airport and airline is currently advising.
If you're already at the airport, keep an eye on display screens.
This article will continue to be updated with all the latest information you need if you're due to travel.
You can also follow our live blog which will have updates on what's going on.
What are my rights if my flight is delayed?
Disruption to air traffic control counts as an "extraordinary circumstance".
That means it is out of the airline's control - so they don't have to offer compensation.
But if your short-haul flight (under 932 miles) is delayed by two hours or more, airlines must offer assistance under UK law.
For longer flights up to 2,175 miles, the delay must be more than three hours to qualify, and for long-haul flights going further than that, the delay must reach four hours to get assistance.
They have a duty to provide:
• two free phone calls, faxes or emails (often by refunding the cost of your calls)
• free meals and refreshments appropriate to the delay (often in voucher form)
• free hotel accommodation and hotel transfers if an overnight stay is required.
Sometimes airlines may be unable to provide assistance to all passengers, particularly where staff are stretched - which could be the case with the mass delays we're seeing after the air traffic glitch.
If this is the case, the Civil Aviation Authority says passengers should organise their own assistance and claim the cost back later.
"If you end up paying for things yourself, keep every receipt and do not spend more than is reasonable," its website says.
It cautions airlines are unlikely to reimburse for alcohol or luxury hotels. Some airlines provide guidelines on what counts as reasonable expenses.
Whatever the reason for the delay, you are entitled to a full refund if you decide to abandon your journey after five hours of delays.