A "technical issue" has hit UK air traffic control systems, with airlines warning of delays to flights.
Britain's National Air Traffic Services said it was experiencing "technical issues" and has "applied traffic flow restrictions to maintain safety".
"Engineers are working to find and the fix the fault. We apologise for any inconvenience this may cause."
They did not provide any further information about what caused it or how long it would take to fix.
Earlier Scottish airline Loganair said on social media site X, formerly Twitter, there had been a network-wide failure of UK air traffic control computer systems, warning some flights may face delays.
Broadcaster Gabby Logan also said on X she was on a plane on a runway at Budapest airport, and had "just been told UK airspace is shut", adding "we could be here for 12 hours".
Emmet Lyons, a journalist for BBC's US partner CBS News, said he had received an update from EasyJet while sitting on the tarmac in Spain.
The airline said it the air traffic control issue was "currently affecting all flights due to fly into or out of United Kingdom airspace".
"We are working with the relevant authorities to understand the impact of this issue and the timescale for normal operations to resume," it said.
