| Answer | Crossword Clue |
|---|---|
| MACH | It's calculated relative to the speed of sound |
| MACH | Measure of speed relative to sound |
| MACH | Term referring to the speed of sound. |
| SONIC | Of a speed equal to the speed of sound. |
| YEAGER | First pilot to fly faster than the speed of sound |
| CHUCKYEAGER | First pilot to travel faster than the speed of sound |
