Defense officials on Friday said they were suspending all F-35 flights after engineers at Edwards Air Force Base in California found a crack on an engine blade during a routine inspection.

“It is too early to know the fleetwide impact of the recent finding,” the Pentagon said in a statement. Officials planned to ship the engine’s turbine module and associated hardware to manufacturer Pratt & Whitney’s engine facility in Middletown, Conn., for evaluation.

The F-35 Joint Program Office is working closely with Pratt & Whitney and Lockheed Martin at all F-35 locations to ensure the integrity of the engine, and to return the fleet safely to flight as soon as possible,” the Pentagon statement said. Lockheed Martin is the prime contractor; Northrop Grumman and BAE Systems are principal partners.

The $400 billion Lightning II multi-role fighter has been plagued with cost overruns and performance problems. Last year, the Government Accountability Office reported that unit costs per aircraft have doubled since development began in 2001 and full-rate production has slipped six years to 2019.

“Critical dates for delivering warfighter requirements remain unsettled because of program uncertainties,” GAO auditors wrote. “Affordability is a key challenge–annual acquisition funding needs average about $12.5 billion through 2037 and life-cycle operating and support costs are estimated at $1.1 trillion. DOD has not thoroughly analyzed program impacts should funding expectations be unmet.”

In September 2012, Maj. Gen. Christopher Bogdan, then the deputy program manager, called the relationship between Lockheed Martin and the program office “the worst I have ever seen.” The comment drew headlines and provoked the ire of Lockheed executives, but Pentagon officials supported Bogdan and he now leads the program.

The F-35 is the most expensive weapons program in history.