Air traffic controllers warned travellers last night of 'substantial' flight delays for up to a month after the opening early today of the new Swanwick radar centre.

More than 1,000 flights a day could be at least an hour late after the £650 million Hampshire centre - itself delayed for five years - starts work and is monitored for glitches, staff told The Observer. Final preparations were 'a shambles', one said.

A senior controller due to work the first shift, when control of traffic was being handed over to Swanwick from an obsolete centre near Heathrow at 2.30am, said staff had been rostered for back-to-back shifts in breach of safety rules. This meant shortened rest periods.

'Obviously those will have to be changed. They will not be worked and there will be no threat to safety, but it is a sign of the chaos down here,' one controller said.

Sources said it would take until the end of February for staff to get used to the system, with training still taking place. The centre was due to open in 1996 at a cost of £425m, but thousands of glitches caused hold-ups and raised the cost by 50 per cent

The centre is badly needed for safety reasons to handle overcrowding in the skies.