Douglas designed the X-3 with the goal of a maximum speed of approximately 2,000 m.p.h, but it was, however, seriously underpowered for this purpose and could not even exceed Mach 1 in level flight.
Douglas merancang X-3 dengan tujuan kecepatan maksimum sekitar 2.000 mph, tetapi yang terjadi adalah underpowered serius dan bahkan tidak bisa melebihi Mach 1 di tingkat penerbangan.