Boeing is seriously considering protesting the US Air Force decision to award a $35bn contract for refuelling tankers to EADS, the European defence company, the company said late on Friday.

The Chicago-based company expressed “significant concerns” about the process used to select EADS and Northrop Grumman, its US partner, following an air force briefing on Friday. “We left the room with significant concerns . . . including programme requirements related to capabilities, cost and risk, evaluation of the bids and the ultimate decision,” said Mark McGraw, Boeing’s tanker programme manager.