The DoD and Administration have decided the F135 is the right engine for the F-35

In the competition that took place in the early 90s, (DARPA ASTOVL) both Lockheed Martin and Boeing selected Pratt & Whitney engines to power their offerings. McDonnell Douglas’ offering had a GE powered gas driven lift fan concept. In 1995, the DARPA ASTOVL program became the JAST program when funding shifted from DARPA to the Navy/Air Force budget and then became the Joint Strike Fighter Concept Demonstrator Program. At this point, all three airframers maintained their engine selections in their concept demonstration aircraft. The McDonnell Douglas gas driven lift fan concept with the GE engine continued into CDA. However, MD became concerned about the gas driven lift fan concept and so developed a second concept consisting of a P&W main engine (a stock F119) and a GE lift engine. MD ultimately discarded the gas driven lift fan concept prior to the final JSF CDA down select which they lost to Boeing and Lockheed Martin. Competition took place at the contractor level, and all three airframers who ultimately submitted proposals to the CDA program considered which engine would provide them the best advantage to win the competition based on the requirements set forth in the RFP, and ultimately all three airframers selected P&W engines. The Lockheed Martin X-35 won the final JSF System Design and Demonstration competition powered by a P&W engine. The DoD and two Presidential administrations have since determined that further competition is unnecessary and not in the warfighters’ or taxpayers’ best interests.