UK flight schedules resume amid warning of further delays
Passengers are being advised to check their flight's
status
Airline passengers have been warned
there could be further disruption today due to Saturday's technical fault at the
National Air Traffic Service.
Hundreds of flights were delayed or cancelled and Nats said there might be a knock-on effect for services.
But airports across the UK say they are hoping to return to normal operations after the telephone glitch.
The software failure at Nats Swanwick centre in Hampshire was fixed after about 12 hours.
Thousands of passengers faced cancellations and long waits after the Nats internal phone system broke down, resulting in it being able to handle about 20% fewer flights than on a normal Saturday.
Nats announced at 19:30 GMT on Saturday that the problem had been resolved.
Juliet Kennedy from Nats said controllers were now able to manage normal levels of traffic, but added passengers could potentially continue to experience some delays because of the earlier problems.
"The system from an air traffic perspective is already back to normal," she told the BBC.
"I recognise of course that airlines have their schedules disrupted because they end up with aeroplanes in the wrong place so it may take them some time to restore their operation to normal."
Lisa Smith, who is trying to travel to Lapland with her son Thomas, was among those still facing delays at Norwich Airport.
"We came here two years ago to go and the plane was delayed then and then it was cancelled because there was too much ice on the runway, so it's a little bit like deja-vu," she said.
The worst-affected airport, Heathrow, which had cancelled 228 flights by 18:55 GMT on Saturday, said there were no planned changes to its schedule.
But along with many other airports it was advising passengers to check their flight's status before travelling.
Airports affected on Saturday also included Gatwick, Stansted, Cardiff, Belfast and Glasgow.
Thousands of travellers experienced delays and
cancellations to their flights on Saturday 
Many, like this woman taking a nap at Gatwick, found
ways to pass the time 
After a frustrating Saturday, Stansted forecast a
normal flight schedule for Sunday By 16:00 GMT on Saturday, Nats said it had handled 2,576 flights compared with 2,905 at the same time last week.
Ryanair said 300 of its flights had been delayed on Saturday with 12 cancelled, and called on the Civil Aviation Authority (CAA) to act.
"While we acknowledge problems can occur, where is the contingency?" it said in a statement.
By Saturday evening Gatwick airport said it was
"returning to normal operations". A spokeswoman said it was "not expecting
serious disruption" on Sunday.
Delays at Stansted averaged two to four hours, a spokeswoman for the airport said, adding that schedules were expected to return to normal on Sunday but warning there could be "minor delays".
Eurocontrol - which manages European air safety - said around 1,300 flights, or 8% of all air traffic on the continent, had been "severely delayed".
Belfast International Airport and Dublin Airport both reported a number of cancellations.
Manchester Airport had been "only minimally affected" by the problem while Leeds Bradford, Birmingham, Doncaster Robin Hood and Newcastle airports all reported minor delays, with flights to London worst affected.
The glitch meant Nats could handle about 20% fewer
flights than a normal Saturday Nats said the problem at Swanwick arose in the early hours of Saturday morning when the night-time operation failed to properly switch over to the daytime system.
The software failure happened when the 23 controllers working overnight were due to hand over to the 125 on the day shift at around 06:00 GMT.
The problems prevented staff opening new control positions to deal with busier daytime traffic.
A Nats spokesman said controllers used the system to speak to other air traffic agencies both in the UK and Europe and it was "very complex and sophisticated... not simply internal telephones".
The BBC's transport correspondent Richard Westcott said it was a totally different issue to a software problem that saw flights in southern England delayed due to "technical problems" in July.
