A B-2 Stealth Bomber sits on the tarmac at the Palmdale Aircraft Integration Center of Excellence in California, where the U.S. Air Force and manufacturer of the B-2, Northrop Grumman, celebrated its 25th anniversary July 17, 2014. Frederic J. Brown/AFP/Getty Images

Boeing and Lockheed Martin filed a joint protest Friday asking the U.S. Government Accountability Office to review the Pentagon's decision to award the recent $80 billion Long Range Strike Bomber contract to Northrop Grumman at the end of October. The two rivals, who launched a joint bid to win the bomber contract, contend that Northrop's winning aircraft will join a long list of "prohibitively expensive trends" that have soured past defense acquisitions.

"Boeing and Lockheed Martin concluded the selection process for the Long Range Strike Bomber was fundamentally flawed," read a statement from the two U.S. defense giants. "The cost evaluation performed by the government did not properly reward the contractors’ proposals to break the upward-spiraling historical cost curves of defense acquisitions, or properly evaluate the relative or comparative risk of the competitors’ ability to perform, as required by the solicitation."

It's believed that Northrop won the contract because its aircraft per unit came in at $511 million, far below the Pentagon's cap of $550 million per unit, according to a Defense News report. Boeing and Lockheed claim that this price will increase significantly as Northrop overruns on the contract's budget.

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While Boeing is mounting the protest jointly with its defense rival Lockheed, the Chicago-based company, which is better known for its commercial aircraft manufacturing plants in Seattle, has had some success in protesting defense decisions in the past. In 2011 Boeing successfully overturned a decision by the Pentagon to award a $43 billion contract for the KC-46 air-refueling tanker to the French airline company Airbus.

While Lockheed is largely unaffected by losing out on the bomber contract because of its huge $1.5 trillion F-35 Joint Strike Fighter deal, which is set to last until 2055, Boeing's military aircraft facility in St. Louis faces a far more uncertain future. The two aircraft it currently manufactures there, the F-15 Eagle and the F/A-18 Super Hornet, are coming to the end of the their manufacturing lives by the end of the decade. Winning the bomber contract would have brought in decades of revenue and ensured that jobs would be saved.

The Government Accountability Office now has 100 days to respond to Boeing and Lockheed's joint protest.