The chaos that hit UK airports is clearing - but 38 more flights have been cancelled at Heathrow.
While air traffic control company Nats says its systems are now fully operational, the flight mayhem at some of the nation's busiest thoroughfares could still be a reality for some passengers on Saturday.
Dozens of flights were cancelled and many others delayed after a computer failure at Nats' company headquarters on Friday.
A Heathrow spokesman said 38 flights were cancelled before 9.30am on Saturday "as a knock-on from yesterday".
"Although operational restrictions applied during the failure have been lifted, it will take time for flight operations across the UK to fully recover so passengers should contact their airline for the status of their flight," Nats said.
"We apologise for the impact that this issue has had, and the delays and inconvenience caused."
The company has ruled out a power outage as the source of the glitch at Nats' STG700 million ($A1.28 billion) centre.
Airports as far north as Aberdeen and Edinburgh were affected by the computer problem.
Other airports that reported delays yesterday afternoon included Manchester, Stansted and Luton.