It will be staffed by 800 controllers and will largely replace the work done at West Drayton in West London.

We have been encouraged by the pace of progress

Nats spokesman

The Hampshire centre was due to open in 1996 at a cost of around �350m.

But a spokesman for the National Air Traffic Services (Nats) said a project the size of Swanwick was always likely to take longer than expected.

"We have been encouraged by the pace of progress and dates have now been set," he said.

The technical handover is now due to take place in December this year.

Accidents

The delay meant a large increase in the number of flights being handled by West Drayton, which led to concerns about controllers' workload.

MPs on the transport committee were worried it would result in a greater risk of accidents.

A House of Commons select committee criticised air traffic control chiefs over the delay and called for an independent study to see whether the Swanwick centre should be scrapped altogether.

But Nats always maintained that West Drayton could safely handle flights for some time and that safety was not being compromised.

The Swanwick centre, which will serve England and Wales, is intended to replace both the West Drayton centre, in Middlesex, and one in Manchester.

West Drayton will continue to handle flights to and from Heathrow airport.