Swanwick's entry into service represents a remarkable technical achievement

Nats' Richard Everitt

The complexity of the move from West Drayton, near Heathrow, to Swanwick is expected to cause delays to flights for some days, the head of the recently part-privatised National Air Traffic Services (Nats) has warned.

As the new operation got underway, Nats' Chief Executive Richard Everitt, praised the successful switch-over, describing it as "is one of the largest and most complex logistical transitions in air traffic history".

Flight capacity is being reduced this weekend in case of unforeseen problems with computer systems as Swanwick begins operation.

Travellers are likely to experience delays, particularly on domestic and European flights, in the first 10 days of the �623m centre.

Safety fears

Most passengers at Heathrow on the new system's first day accepted the need for caution, although none reported problems with their journeys.

Briton Andrew Jones, 35, said his flight to Prague had not been affected so far.

"I have been worried about whether it would be safe because of the congestion in the air.

"I hope it's going to be regulated properly. Railtrack was such a shoddy operation with the Paddington rail crash, we can't afford to have the same thing with planes."

Swanwick statistics

Largest purpose-built air traffic centre in the world Controls 200,000sq miles of airspace above England and Wales 644 staff trained to operate and maintain the system Airspace split into over 30 flight levels Will handle 2m flights a year, rising to 3m by 2012 6,000 flights a day at height of summer

IT expert Dave Fox, 54, from Hyde, Cheshire, said it was vital to bring in the improved technology to avoid the situation in the US where ageing equipment was controlling the air space.

Until it went operational the switch to Swanwick was fraught with difficulties.

The much-anticipated project went hugely over budget - 50% more than projected - and is finally opening after a six-year delay.

It also coincides with the introduction of a new flight separation system by European controllers, which is expected to add to problems.

Extra capacity

Mr Everitt said the new centre was a "tremendous achievement".

"We're bringing it in very carefully, as you would expect us to do as a safety critical organisation, and that will mean that our controllers will be given time to bring on the capacity that this offers," he told the BBC.

"There will be some delays but we've worked very carefully with the airlines to try and ensure they're kept to a minimum."

But Don Foster, Liberal Democrat transport spokesman, said the introduction of the new system had been "unsatisfactory from beginning to end".

"It is a pretty ridiculous situation when delays which must have been known about are only announced as the new system is introduced," he said.

Swanwick's opening follows last year's part-privatisation of Nats, with 46% of the company being taken over by an airline consortium which includes British Airways and Virgin Atlantic.

'More needed'

Christopher Darke, general secretary of the British Airline Pilots Association (Balpa), welcomed the new centre.

But he called on Nats and the government to unfreeze development of a new control centre at Prestwick in Scotland, put on hold after 11 September.

He warned the UK needs two modern centres to compete for future air traffic contracts under the Single European Sky initiative, when all European air traffic control is integrated.