The US Air force is open to making changes in the draft request for proposal (RFP) for the KC-X aerial tanker programme.

The USAF initially planned to acquire 179 tanker aircraft to replace the existing KC-135s through the deal estimated to be worth $35bn.

The draft presently includes 373 pass / fail threshold requirements for participants.

The RFP, however marks a shift from previous attempts to procure the 179 tankers since the Pentagon is pursuing a fixed-price development contract and production profile.

USAF secretary Michael Donley was quoted by Aviation Week as saying that they are going to consider some changes to the RFP.

“We think it is a strong RFP and we think the main outlines of it are very well [put] together. But, we continue to get questions,” he said.

The RFP is the air force’s re-attempt to acquire aerial tankers, which was cancelled last year after government auditors upheld a challenge from Boeing over unfairness of the contract given to Northrop.