Multiple choice

An aircraft flying at mach number ___ will be considered to be flying at subsonic speed.

  1. 1.2

  2. 1.1

  3. 1.0

  4. 0.9
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Subsonic speed is defined as speed below Mach 1.0 (the speed of sound). Mach 1.0 is exactly the speed of sound (transonic region). Mach numbers greater than 1.0 (1.1, 1.2, etc.) are supersonic speeds. Only Mach 0.9 is below Mach 1.0, making it the only subsonic option. The question tests the definition of subsonic versus supersonic flight regimes.

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