Definition
The classification of aircraft flight speeds into bands defined by the aircraft's velocity relative to the local speed of sound (Mach number). The standard ranges are subsonic (below approximately Mach 0.75), transonic (approximately Mach 0.75 to 1.20), supersonic (approximately Mach 1.20 to 5.00), and hypersonic (above Mach 5.00). These ranges are based on aerodynamic behavior, not just numerical speed, because airflow over the airframe changes character as the aircraft approaches and exceeds the speed of sound.
Plain English
Aircraft speeds are grouped into four bands based on how fast the aircraft is moving compared to the speed of sound. Each band has its own airflow behavior, which is why pilots and engineers categorize them this way rather than just using miles per hour.
Context Anchor
Seen in aerodynamics discussions about subsonic versus supersonic flow, especially when learning how aircraft handling and airflow change as speed increases.
Derivation
“Speed” means rate of motion. “Range” here means a band between limits, not distance. So a speed range is a band of speeds grouped together because they share similar flight and airflow behavior.
Why Pilots Care
Each range produces distinct changes in lift, drag, and control that affect aircraft performance and safety limits.
Intuition Check
Do not read “speed ranges” as just “slow, medium, and fast.” In this FAA context, the ranges are tied to the speed of sound and to changes in airflow around the aircraft.
Example Sentence 1
Most general aviation aircraft operate entirely within the subsonic speed range, while modern airliners cruise in the high subsonic range just below the transonic threshold.
Example Sentence 2
Pilots must understand supersonic speed ranges before attempting flight above Mach 1.2.