On Friday, officials discovered a crack in the jet engine turbine aboard one of test versions of the Air Force variant of the F-35 aircraft being flown at Edwards Air Force Base, Calif., program spokeswoman Kyra Hawn said in a statement.
"It is too early to know the fleet-wide impact of this finding, however as a precautionary measure, all F-35 flight operations have been suspended until the investigation is complete and the cause of the blade crack is fully understood," Hawn said.
Aside from the United States, the United Kingdom, Canada, Italy, the Netherlands, Turkey, Australia, Denmark and Norway are all scheduled to buy versions of the F-35 for their armed forces.
Friday's announcement comes after DOD and military officials recently restarted test flights for the Marine Corps version of the fighter.
All flight operations for those jets were suspended in January after key components on the exhaust system on the fighter's single engine failed during a test flight at Eglin Air Force Base, Fla.
The malfunction occurred just before the plane was about to take off, according to recent news reports. The pilot was able to safely abort the training flight, and the failure did not result in any injuries to the pilot or the ground crew at Eglin, according to reports at the time.
Friday's grounding was also caused by malfunctions in the fighter's jet engine, built by Pratt & Whitney.
The faulty engine is en route to the company's facility in Middletown, CT where Pratt & Whitney officials "to conduct more thorough evaluations to determine the cause of the [malfunction]," company spokesman Matthew Bates said in an email to The Hill.
"As a precautionary measure, all F-35 flight operations have been suspended until the investigation is complete and the cause of the blade indication is fully understood," he said.
Company officials are "working closely with the F-35 program office" as well as fighter jet program's prime contractor, Lockheed Martin, to resolve the engine malfunctions and "return the fleet safely to flight," Bates said.
That joint inspection team "is focused on ensuring the integrity of the engines across the entire fleet so the F-35s can safely return to flight as soon as possible," according to a Lockheed Martin statement issued Friday.
Former Defense Secretary Robert Gates put the program's Marine Corps variant, known as the F-35B, on “probation” and threatened to cancel it unless its cost and schedule problems were fixed within two years.
in 2011, Defense Secretary Leon Panetta officially took the Marine Corps plane off probation. Recent reports, however, claim the jet fleet, considered the most expensive acquisition program in Pentagon history, is currently $150 billion over budget, based on initial cost estimates.
With a total cost estimates at over $400 billion, the F-35 is the most expensive weapon development program in the history of the Pentagon.