National Air Traffic Services (Nats) is trying to buy-out air traffic controllers' holidays to cope with the training requirements for the New En Route Centre at Swanwick.
Air traffic controllers, members of the IPMS trade union, are currently balloting on whether to accept the offer to buy back up to 10 days annual leave.
The dispute erupted as the air traffic service reached a significant milestone in the development of the Swanwick centre with the handover of the computer system on 19 December.
Nats chief executive Colin Chisholm said, "Swanwick has passed it biggest and most important test. When you consider the many difficulties we faced only two years ago, technical handover is a major achievement."
Technical handover was achieved with just six known programme trouble reports, rather than the 50 Nats was predicting last autumn, according to a Nats spokesman.
Nats insisted that no air traffic controllers would be required to forgo holidays or days off in lieu.
The union said the Nats move was prompted by a shortage of air traffic controllers, which Nats denies.
Air traffic controllers who contacted Computer Weekly said Nats would face serious problems if the offer was rejected. They said either training would be delayed, with a possible knock on effect on the planned January 2002 date for Swanwick to become operational, or air travellers would face substantial delays this summer.
A Nats representative said, "We can meet the Swanwick operational date even if the offer is not taken up."