A B-2 Spirit lands at Andersen Air Force Base, Guam, on Sunday, April 30, 2006. B-2s are replacing the B-1B Lancers at Andersen as part of the continuous bomber rotation. (U.S. Air Force photo/Airman 1st Class Michael S. Dorus)

The Government Accountability Office on Tuesday denied a protest of the $80 billion contract awarded to Northrop Grumman to build the Air Force’s next-generation bomber, allowing the program to proceed.

Boeing and Lockheed Martin, which had teamed up to bid on the project, had argued that the Air Force’s selection process was “fundamentally flawed.” But the GAO rejected that, saying “the technical evaluation, and the evaluation of costs, was reasonable” and adhered to procurement regulations.

Late last year, the Air Force awarded the contract to build what is known as the Long Range Strike Bomber, a highly classified program of a fleet of stealthy aircraft capable of carrying nuclear weapons deep into enemy territory. The program is one of the Air Force’s top acquisition priorities, and the contract is likely to be one of the most significant the Pentagon awards over the next decade.

In announcing the contract last year, Defense Secretary Ashton B. Carter said the program represents a “technological leap” that will allow the U.S. to “remain dominant.”

The companies were competing to build 100 of the planes, which should enter service in the 2020s. The new bomber would eventually replace the Pentagon’s aging fleet of bombers, such as the B-52 and the B-1. The win was a huge victory for Northrop, which also built the stealthy B-2 bomber.

[Northrop Grumman may have won the Long Range Strike Bomber, but now the real work begins.]

The GAO did not release any other information on its decision, saying that “the details of Boeing’s challenges, and GAO’s decision resolving them, are classified.”

In a statement, Boeing officials said that, “we continue to believe that our offering represents the best solution for the Air Force and the nation, and that the government’s selection process was fundamentally and irreparably flawed.”

The company said it would review the decision and decide whether it would pursue further action “in the coming days.”

Randy Belote, a Northrop spokesman, said the GAO’s decision “confirms that the U.S. Air Force conducted an extraordinarily thorough selection process and selected the most capable and affordable solution.”

The GAO’s ruling comes just days after the Air Force removed Richard W. Lombardi, a senior acquisition official, after he revealed that he had not disclosed that his wife has a retirement account from Northrop. Air Force Secretary Deborah Lee James referred the case to the Pentagon’s inspector general.

Lombardi was not a part of the team that selected Northrop Grumman’s design for the new bomber, Air Force officials said. But he did serve as a top weapons buyer for the Air Force since May 2014. Lombardi previously served from September 2012 to April 2014 as the Air Force’s deputy assistant secretary for acquisition integration in Washington.