I realize "mean time between failures" doesn't mean what I think it means, but holy moley. The engine can only go 25 hours between failures instead of the 120 t

I realize "mean time between failures" doesn't mean what I think it means, but holy moley. The engine can only go 25 hours between failures instead of the 120 they're aiming for? That's a pretty big gap in performance and I wouldn't want to be flying one of these things. "As of late December, engines on the Marine Corps’ complex version of the F-35, designed for short takeoffs and vertical landings, flew about 47 hours between failures caused by engine design issues instead of the 90 hours planned for this point, according to GAO officials. Air Force and Navy model engines flew about 25 hours between failures instead of the 120 hours planned."