New design changes raises pressure on future of F-35B variant

Lockheed Martin and Pratt & Whitney have revealed the extent of design changes required to release the short take-off and vertical landing F-35B from a newly imposed "probationary" status within two years.

The Joint Strike Fighter programme is now cleared to spend another $4.6 billion partly to correct structural and propulsion design flaws in the F-35B. But patience is swiftly cooling with the specialised variant ordered by the US Marine Corps.

While the US Air Force's conventional take-off and landing F-35A and the US Navy's F-35C carrier variant are "proceeding satisfactorily" in tests, Secretary of Defense Robert Gates says the Marine Corps' prized stealth fighter is "experiencing significant testing problems".

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