Boeing Co. said Monday it plans to formally protest the $35 billion contract awarded to Northrop Grumman Corp. and its European partner to build a new fleet of aerial refueling tankers for the Air Force.

Boeing plans to file the protest Tuesday, at which point the Government Accountability Office will have 100 days review the complaint and rule. The government could overturn the decision, which would force the companies to re-bid for the contract.

"Our team has taken a very close look at the tanker decision and found serious flaws in the process that we believe warrant appeal," said Jim McNerney, Boeing's chief executive, in a statement. "This is an extraordinary step rarely taken by our company and one we take very seriously."

The partnership between Northrop and the European Aeronautic Defence & Space Co., parent of Airbus, was selected Feb. 29 to supply 179 tankers, to be known as the KC-45A, which allow fighter jets and other planes to refuel without landing. The Air Force plans to replace more than 500 aircraft, which could bring the total program value to $100 billion one of the largest defense contracts ever.

The protest, which had been expected in the wake of the surprising decision to bypass longtime tanker supplier Boeing, comes as congressional lawmakers are berating the Pentagon for awarding such an important military contract to a team that includes a European company.

In its defense, Northrop on Monday announced a revised estimate of the number of U.S. jobs that will be supported by its tanker program nearly doubling the total to 48,000 from its original expectation of 25,000. A large portion of those jobs will be located in Los Angeles, which is home to a large aerospace industry. Northrop has identified 41 Southern California aerospace companies that will supply parts to the plane.

Northrop also said Monday that its tanker a modified Airbus A330 performed better than Boeing's proposed plane on four of the five criteria used to evaluate the two bids: capability, price, aerial refueling assessment and past performance. The company did not comment on the final category of proposal risk.

But Boeing has said late changes in the evaluation criteria put its plane at an unfair disadvantage.

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