The U.S. Air Force on Friday declined to confirm that it had received only one bid for a $6.8 billion helicopter competition that closed on Thursday, saying that information was “source selection sensitive.”

All but one of the contractors expected to bid to build a new combat search and rescue helicopters for the Air Force announced last month that they would not compete, raising the prospect that the Air Force would have to adopt a different approach to the acquisition program.

Sikorsky Aircraft, a unit of United Technologies Corp , did submit a bid for the competition, based on its H-60 helicopter, according to a company spokesman. Other potential competitors confirmed that they had decided to skip the bidding, and at least one of the companies said it was exploring a possible legal challenge to the terms of the competition.

Air Force spokesman Ed Gulick declined to say how many companies had submitted bids by the Jan. 3 deadline or whether the Air Force had already initiated steps to reflect that the procurement would now come from a sole source.

“We cannot release as the information is source selection sensitive,” he told Reuters in an emailed statement.

Gulick said the Air Force remained “committed to a fair, open and transparent process” to pick a new, affordable Combat Rescue Helicopter (CRH) that met the military’s requirements.

“To ensure this occurs, we are prohibited from releasing information while in the request for proposal and selection processes. Once we select and announce the final contractor we will be able to openly discuss the details of the CRH program,” he said in an emailed statement.

Lieutenant General Charles Davis, the top military official in charge of Air Force acquisition, told Reuters in an interview last month that the helicopter competition was structured to tell potential bidders exactly what capabilities the Air Force wanted and what it could afford.

He denied that the terms of the competition had been written to favor the Black Hawk helicopter built by Sikorsky, and said Sikorsky would be asked to submit certified cost and pricing data if it turned out to be the sole bidder for the program.