Thousands of people are stranded on aircraft and in airports due to lengthy flight delays caused by a technical failure at UK air traffic control.
More than 500 flights have been cancelled, affecting all UK-based carriers.
National Air Traffic Services is “thoroughly” looking into what went wrong with its flight planning system, which it says was repaired at 15:15 BST.
Short-haul customers are being advised by British Airways to postpone going to the airport until their flight is confirmed to be running.
Other airlines have issued cancellation or delay alerts, including Ryanair, EasyJet, Wizz Air, Loganair, and Aer Lingus.
After noon, Nats issued a statement explaining that they were forced to limit the number of planes they could manage due to a difficulty.
Airports and airlines started alerting customers about prolonged delays and urging them to verify the most recent information before departing.
Its operations director, Juliet Kennedy, explains “the automatic system, which provides controllers with details of every aircraft and its route wasn’t working” and “instead to manage safety we had to limit the number of flights we could manage”.
She says Nats’ teams “worked hard to resolve the problem” but “it will take some time for flights to return to normal”.
“We will continue to work with the airlines and airports to recover the situation,” she says.
“Our absolute priority is safety and we will be investigating very thoroughly what happened today,” Kennedy adds.