Thousands of air passengers have been suffering long delays and cancellations after a “technical issue” hit UK air traffic control systems.
People are stuck in the UK and abroad, after National Air Traffic Services limited the number of planes landing.
Airlines and airports warned there were still “significant delays” despite the issue being fixed within hours.
One passenger told BBC News her afternoon flight was not expected to leave until after midnight.
There have been warnings that some knock-on disruption could last for days.
Heathrow said late on Monday evening that schedules remained significantly disrupted, adding that people travelling on Tuesday should contact their airline before heading to the airport.
Gatwick Airport said it was planning to operate a normal schedule on Tuesday, but advised passengers to check the status of their flight with their airline before going to the airport.
London Luton Airport also said on Monday evening that flights across UK airspace remained subject to delays and cancellation, and people should check with their airline for the status of their flight.
Nats confirmed the fault just after midday on Monday, before it announced at 15:15 BST that it had identified and remedied the issue.
It said “it will take some time for flights to return to normal”.
