The effort involved the design, construction and flight testing of two YF-22 prototype aircraft.

努力参与设计，建造和飞行试验两y f - 22原型机。

youdao

The effort involved the design, construction and flight testing of two YF-22 prototype aircraft.

努力参与设计，建造和飞行试验两y f - 22原型机。

youdao