All F-35 flight operations have been suspended until the investigation is complete, the Pentagon said in a statement on Friday.
"It is too early to know the fleet-wide impact of the recent finding," it said, adding 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 said a routine engine inspection revealed a crack on an engine blade of the F-35 engine installed in F-35A aircraft AF-2 operating at Edwards Air Force Base, California.
Engineering teams are shipping the engine's turbine module and its associated hardware to Pratt & Whitney's Engine Facility in Middletown, Connecticut, to conduct more thorough evaluation and root cause analysis, it said.
The New York Times said the suspension of flights comes at an awkward time for the military, which is facing automatic budget cuts that could slow its purchases of the planes.
The F-35 II is a family of single-seat, single-engine, fifth generation multirole fighters under development to perform ground attack, reconnaissance, and air defense missions with stealth capability.