Pratt & Whitney has delivered the first production model of the F135-PW-600 jet engine to Lockheed Martin for the F-35B short take-off and vertical landing (STOVL) variant.
The 43,000lb-thrust-class engine will be installed in the fifth F-35B flight test aircraft, named BF-5, allowing Lockheed to continue flight tests using a production version of the engine.
The delivery formally completes an eight-year development and testing programme by P&W on the F135 engine family, which includes the F135-PW-100 model powering the conventional take-off (CTOL) and landing F-35A and the carrier-based (CV) F-35C.
The CTOL and CV version of the engine entered production in February, with 10 powerplants already delivered.
Although dedicated engine testing is now complete P&W will continue to support the F-35 flight and ground test phase, which continues through 2016.
Meanwhile, the company will launch production of "the most advanced propulsion systems ever built", says Bennett Croswell, P&W's vice president of F119/F135 engine programmes.
The STOVL version of the engine includes a shaft-driven lift-fan system that provides both thrust and lift, allowing the F-35B to hover.
The US Marine Corps plans to buy 420 F-35Bs to replace the Boeing AV-8B Harrier II and F/A-18 Hornet.