Air traffic controllers have warned the Government that air safety will be compromised unless more cash is found for the part-privatised National Air Traffic Service (NATS).
The call comes after a report by MPs condemned NATS's decision to cut back on safety critical staff.
Prospect, which represents 3,500 NATS controllers and engineers, is says the Government should face up to its responsibility and halve the debt NATS has been saddled with under the terms of the PPP.
David Luxton, the union's aviation officer, said: "As part of NATS' cost cutting measures, the organisation plans to shed 450 system specialist engineering posts over the next five years, increasing to 900 posts over the next 10 years. Yet NATS needs specialist engineering skills to develop and expand.
"NATS' debt level is crippling it both financially and organisationally, detracting from the primary focus of ensuring safe and reliable air travel.
"The Government must step in now to ensure NATS' financial stability so that it can meet its investment plans which are crucial to ensure air traffic safety in the face of the increasing volume of flights."
The Government, however, has so far only offered to match private-sector funding. It has already had to pay up more than the £30 million to bail out NATS's private owners just to keep the service going