Engine Programs for American Sixth Generation Fighter Enter Prototype Stage: Will They Soon Power the F-35?

Engines developed by the firms General Electric Aerospace and Pratt & Whitney being developed for the Next-Generation Adaptive Propulsion program have cleared the U.S. Air Force’s Detailed Design Reviews, which represents a key milestone that allows work to proceed towards building the first prototype ground demonstrators. The two firms are developing competing engines, the respective XA102 and XA103, to power the Air Force’s Next-Generation Air Dominance (NGAD) sixth generation fighter. Although the future of the fighter program remains highly uncertain due to the Air Force’s serious budgetary restrictions, even if work does not proceed the new engines are expected to find applications both on the U.S. Navy’s own sixth generation fighter program, and on the F-35. While General Electric and Pratt & Whitney had previously designed next generation engines for the F-35, which were developed under the Adaptive Engine Transition Program that was terminated in 2023, continued use of enhanced variants of the fighter’s current F135 engine is considered unviable in the long term as its power requirements continue to increase. 

The United States has not developed a clean sheet new fighter engine since the 1980s, with the F119 that powered its first fifth generation fighter the F-22 having first flown in 1990, while the F135 powering the F-35 is a close derivative of that powerplant. Although the disintegration of the Soviet Union prevented the formerly world leading Russian fighter engine industry from gaining a lead over that of the United States, China has rapidly bridged the gap, with its WS-15 engine developed for its J-20 fifth generation fighter expected to have a comparable if not superior weight/thrust ratio to the F135. The need for more efficient engines is considered particularly vital in the Pacific theatre, as not only are fighters required to operate over very considerable ranges, but the integration of new generations of avionics, and possibly of directed energy weapons, has continued to significantly increase power requirements. With both the XA102 and XA103 derived from work on the cancelled Adaptive Engine Transition Program, the possibility remains significant that their primary eventual use will be to re-engine F-35s from the mid-2030s.