"Contrary to the initial tender, which we clearly won two years ago, the current tender is biased in favour of the competition's smaller and less able aircraft," Airbus CEO Thomas Enders told the website of the Financial Times Deutschland.
"It is no longer (a case of) the best plane and no longer fair competition," Enders charged.
Northrop Grumman chief executive Wes Bush said Monday it would withdraw the joint proposal since the US Air Force "clearly favours Boeing's smaller refuelling tanker and does not provide adequate value recognition of the added capability of a larger tanker, precluding us from any competitive opportunity."
Boeing's bid is based on its 767 aircraft, while Airbus and Northrop Grumman planned to use an Airbus A330.
"We are of course very frustrated by this situation," Enders said. "But the real losers are the US army and American taxpayers."
That view was echoed by Alabama Senator Richard Shelby, whose state would have benefited from a promised plant to assemble the Airbus/Northrop tankers that would have created 300 jobs.
"The Air Force had a chance to deliver the most capable tanker possible to our warfighters and blew it," Shelby said.