美国空军负责采购的助理部长Will Roper2020年9月就已经承认Next Generation Air Dominance(NGAD)原型机已经首飞了
In September 2020, Roper stated that a full-scale prototype of the NGAD fighter aircraft has been flown.
https://www.thedrive.com/the-war-zone/36431/the-u-s-air-force-has-flown-a-demonstrator-for-its-next-generation-fighter
The U.S. Air Force Has Secretly Flown A Demonstrator For Its Next-Generation Fighter