The Pentagon has grounded the US military’s entire fleet of F-35 fighter jets after discovering a cracked engine turbine blade in one plane.

The Pentagon has halted flights onboard its fleet of F-35 Joint Strike Fighter jets, causing yet another setback for the US Defense Department’s most expensive weapons program.

Lockheed Martin, the manufacturer of the aircraft and the largest defense contractor in the world, confirmed on Friday that the entire American arsenal of F-35s have been grounded after a routine inspection on a test plane at Edwards Air Force Base in California turned up cracked turbine blade.

The problem was discovered during what the Pentagon called a routine inspection of an F-35A Lightning II, the US Air Force’s version of the new plane.

The US Navy and the US Marine Corps are buying other versions of the F-35, which is intended to replace older fighter jets like the Air Force’s F-16 and the Navy and Marine Corps’ F/A-18.

All versions – a total of 51 planes – were grounded on Friday pending an investigation.

The Pentagon said it was too early to know the full impact of the newly discovered problem.

It said: “On February 19, 2013, a routine engine inspection revealed a crack on a low pressure turbine blade of an F135 engine installed in a CTOL test aircraft at Edwards Air Force Base, Calif.

“Engineering teams are shipping the turbine blade to Pratt & Whitney’s Engine Facility in Middletown, CT, to conduct a thorough evaluation and root cause analysis.

“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.

“The F-35 Joint Program Office is working closely with Pratt & Whitney and Lockheed Martin at all F-35 locations to assess the integrity of the engine, and to return the fleet safely to flight as soon as possible.”

The F-35 is the Pentagon’s most expensive weapons programme, with a total estimated cost of nearly $400bn (£262bn).

The Pentagon has planned to buy more than 2,400 F-35s, but some members of Congress are hesitant due to the hefty price tag.

The UK has ordered 48 F-35s to fly off the Royal Navy’s new Queen Elizabeth carrier once it is built in 2018. Britain has also invested in the development of the jet.