Oct. 28, 2021 New F135 hardware undergoes accelerated mission testing at Arnold AFB The Pratt & Whitney F135 engine, which powers the F-35 Joint Strike Fighter, is back at Sea Level Test Cell 3, or SL-3, at Arnold Air Force Base for another round of accelerated mission testing, or AMT, to validate new hardware.AMT provides a means to put engines through a full life cycle of