Question

Supersonic plane fly with the speed

Answer 1

Supersonic plane fly with supersonic speed.
Supersonic speed is the speed which is greater than the speed of sound(approximately 340 m/s). It is measured in mach numbers.

$Mach\ number= \frac{speed\ of\ air-craft}{speed\ of\ sound}$

Answer 2

Supersonic plane fly with the speed that exceeds the speed of sound.

Such speeds are  represented by Mach no.