Max speed: 305 mph, 565 mph at 32,000'. Service ceiling: 42,000'. Approach speed: 150 mph. The task seemed easy...modify Democratic's P-37A Lightningbolt with a jet engine, tricycle gear and a nose intake to produce a robust hround attack jet with high performance. While 150 mph faster at altitude, low altitude performance was actually worse and the new jet had unusually long takeoff rolls. However, aircrew appreciated the sturdy fighter. Interestingly, the F-97A with a swept wing and control surfaces of the same area experienced absolutely no performance gains, throwing into disarray supersonic compressibility theory and years of aerodynamic research and theory!