That is the warning issued by Prospect, the union representing over 3,000 air traffic controllers, engineers and specialists.
The caution comes in advance of next week's budget, and amid growing media speculation following investment bank Rothschild's appointment as adviser to the Airline Group, that the government and the Airline Group are set to announce a sell-off of its controlling stake in NATS.
Garry Graham, Prospect National Secretary for Aviation stated: "We have been consistent in arguing the need for the government to remain a key shareholder within NATS. Air traffic control is a vital part of the UK's infrastructure. A safe, efficient and effective air traffic control system is of crucial importance not only to the UK economy but also to every member of the travelling public.
"Not one argument has been put to us as to how or why a sell-off would be in the interests of air traffic management service delivery or the public. NATS receives no public subsidy, is a net contributor to the Exchequer and provides an invaluable public service.
"We are concerned that the drive to sell a controlling stake is driven by a short-term and short-sighted desire to raise cash, as opposed to a strategic and long-term view as to what is in the best interests of safe and sustainable air traffic service provision."
Graham said any action by the government to radically reduce its 49% holding is likely to trigger a similar response from the Airline Group, opening the door to an outside buyer at a time when it is vital the UK has an authoritative voice in Europe to shape the future of air traffic management service provision.
"It could lead to greater instability with a drive for profits and dividends undermining the very significant strides which have been achieved in relation to safety, service delivery and increases in capacity," said Graham.