Boeing said on Friday it would seriously consider challenging a US Air Force snub that gave a $35 billion aerial-refuelling programme to a team that includes its European archrival Airbus.

Company executives said they had "significant concerns" about the contract decision after an Air Force briefing on the victory by a team made up of Northrop Grumman Corp and Airbus parent EADS.

These concerns include "evaluation of the bids and the ultimate decision," said Mark McGraw, programme manager for Boeing's tanker, based on the company's 767 commercial airliner.

"What is clear now is that reports claiming that the Airbus offering won by a wide margin could not be more inaccurate," he added in a statement.

Chicago-based Boeing said it would take the next few days to evaluate the data presented by the Air Force and will give "serious consideration to filing a protest".

A week ago, the Air Force announced the winner in the $35 billion program to supply 179 tankers over 15 years. Tankers are used to extend warplanes' range by refuelling them in mid-air.

US Air Force Secretary Michael Wynne told a congressional panel on Wednesday that the Northrop-EADS tanker was "clearly a better performer".

Ultimately, the Air Force plans to replace more than 500 of its current KC-135 tankers, built by Boeing and averaging 47 years old. Boeing now has 10 calendar days to file a protest with the Government Accountability Office, the audit and investigative arm of Congress.

The GAO would have 100 days to make a recommendation to the Air Force. If it found a problem in the selection process, it could urge a new competition be held. McGraw said Boeing executives would work through the weekend to decide on a course of action early this week.

Challenging the decision by its biggest customer would be a gamble for Boeing, which must weigh the risk of losing again, or winning and angering European airline customers.

On his campaign plane on Friday, Senator John McCain of Arizona, the presumed Republican nominee for US president, defended a push he led that derailed a post-September 11 Air Force plan to lease and then buy 100 modified Boeing 767s as tankers.

The deal collapsed in 2004 amid a procurement scandal that sent the Air Force's former No. 2 arms buyer, Darleen Druyun, to prison for negotiating a job with Boeing even as she oversaw billions of dollars of Boeing's weapons programmes.

Boeing's then chief financial officer, Michael Sears, also went to prison and Phil Condit, then chief executive, resigned in fallout from the deal McCain called a taxpayer "rip-off".

The Congressional Budget Office, in an October 16, 2003, report for the Senate Armed Services Committee, estimated savings of $6.7 billion for an outright Defense Department purchase of the 100 Boeing tankers then at issue.