A Marine F-35B Joint Strike Fighter lifts off from the runway during the first short take-off and vertical landing mission at Eglin Air Force Base, Fla., on Oct. 25, 2013. (Samuel King Jr./U.S. Air Force photo)

When the Marine Corps put its version of the F-35 Joint Strike Fighter through a series of tests aboard an amphibious assault ship last spring, officials said that the aircraft performed so well that the service soon declared it ready for combat.

But the Pentagon’s top weapons tester said in a report in July that the exercise was so flawed that it “was not an operational test … in either a formal or informal sense of the term.” Furthermore, the test “did not — and could not — demonstrate” that the version of the F-35 that was evaluated “is ready for real-world operational deployments, given the way the event was structured.”

For the test, which happened in late May aboard the USS Wasp, to be “bona fide,” it would have had to be under “conditions that were much more representative of real-world operations than those that were used during this deployment,” J. Michael Gilmore, director of the Pentagon’s Operational Test and Evaluation Office, wrote in a memo.

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The memo, which had been previously reported on by Bloomberg, was released Monday by the Project on Government Oversight, which said it obtained the document through the Freedom of Information Act.

Among the problems Gilmore cited were the lack of other types of aircraft in the test, which would share space on the flight deck and ground support equipment. He also noted that “key combat mission systems were not installed in the aircraft or were not cleared for use.”

During the tests, the F-35s were “not cleared to carry or employ any ordnance,” Gilmore wrote. And he said that uniformed personnel “received significant assistance from embarked contractor personnel who would not be part of combat operations.”

The Marine Corps did not immediately respond to a request for comment.

Aboard the Wasp in May, Lt. Gen. Jon Davis, the Marine Corps deputy commandant for aviation, said in an interview that, “by all accounts [the test] was a great success. No show stoppers at all.”

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The testing, which was designed to see how the fighter would perform in operational conditions, was hailed as a moment of triumph for the embattled F-35 program, the most expensive weapons system ever developed by the Pentagon. And the successful completion of the test was heralded as a sign that the $400 billion program had turned the corner after years of setbacks, billions of dollars of cost increases and delays.

The program is “building momentum and a very good momentum, and I see very little to discourage me,” Davis said in May.

But in addition to problems with the testing, Gilmore’s office found that the F-35s used in the tests had their own problems.

“Aircraft reliability was poor enough that it was difficult for the Marines to keep more than two or three of the six embarked jets in a flyable status on any given day,” he wrote.

Another section of the report said that the “number of flight hours flown by each aircraft varied widely, with some aircraft in a down status for up to five days in a row, and other aircraft rarely requiring major maintenance.”

Gilmore suggested that the Marines conduct another test with “a more aggressive set of demonstration objectives.”

That recommendation didn’t seem to carry much weight, however. About a week after Gilmore submitted his memo, the Marine Corps declared that the F-35 was “ready for worldwide deployment.”

The F-35, manufactured by Bethesda-based Lockheed Martin, comes in three variants, for the Marine Corps, Navy and Air Force. The Air Force variant is expected to be declared ready for combat sometime late next year, the Navy’s in late 2018 or early 2019.

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