Public concerns could resurface over foreign control of British airspace, Prospect has warned, after the government signalled the possible sale of its share in air traffic control provider NATS.

Buried away on page 74 of Wednesday’s spending review document, the government revealed it would “explore the sale” of its 49% shareholding, as well as looking at options to bring private capital into Ordnance Survey, where Prospect also has members.

“We believe there may be legal obstacles to the sale and we are looking back at the measures taken in 2001 when NATS was part-privatised through the creation of the Public-Private Partnership,” said Steve Jary, the union’s national secretary representing NATS staff.

“If NATS stock comes to be openly traded, there will be nothing to stop a foreign buyer taking it over ­– most likely, a state-owned company or a sovereign wealth fund. This would put the UK in a uniquely vulnerable position. NATS is already the only ‘for profit’, privatised national air navigation service provider in the world.

“Competition in the market for air traffic control towers in the UK has already resulted in the impending transfer of responsibility for air traffic control at Gatwick from NATS to a subsidiary of German-government owned DFS. NATS can’t compete for German towers because the German government does not allow it.”

It is only three years since the government last considered selling its stake in NATS. The reasons it gave then for retaining control – the strategic importance of NATS to the UK and its role in the development of the Single European Sky project – still hold true.