Pratt & Whitney's STOVL F135 engine receives initial service release

Pratt & Whitney has achieved initial service release (ISR) for the short take off and vertical landing variant (STOVL) F135 engine, marking another major milestone. The propulsion system is now certified as the production configuration and cleared for flight in the Lockheed Martin F-35B stealth fighter. Pratt & Whitney received ISR for the conventional take off and landing/carrier variant (CTOL/CV) F135 engine in February 2010.