The US F-35 Joint Strike Fighter program is under fire yet again, with leaks of an upcoming report revealing some shocking shortcomings.

A day after the acting US defense secretary called into question the performance of the fifth-generation stealth fighter jet, Bloomberg released details of a Pentagon report scheduled to be released this week.

Among the troubling findings is the estimated service life of the aircraft, which data suggests “may be as low as 2,100” fleet hours, versus the expected service life of 8,000.

“Interim reliability and field maintenance metrics to meeting planned 80% goal not being met,” according to the report, which translates into decreased availability for training. “Current fleet performance ‘well below’ that benchmark.”

The assessment also pointed to cybersecurity vulnerabilities that have not been resolved and problems with computerized maintenance tools.

Pilots and maintenance personnel “must deal w pervasive problems w data integrity, completeness on a daily basis,” one tester was quoted as saying.

On Tuesday, acting US Secretary of Defense Patrick Shanahan was pressed to clarify his previous criticisms of the F-35 program, and whether he was biased due to his ties to a competitor of F-35 manufacturer Lockheed Martin.

“I am biased toward performance,” Shanahan told reporters. “I am biased toward giving the taxpayer their money’s worth. And the F-35, unequivocally, I can say, has a lot of opportunity for more performance.”

Shanahan previously worked as an executive for Boeing, which is reportedly hoping to sell its F-15 fighters to the Pentagon.

The F-35 program has long been plagued with criticisms of its costliness and development delays.