Cruising speed is the steady speed an aircraft holds during the main part of a flight at altitude. For most commercial jets this is around Mach 0.78 to 0.85 — roughly 830 to 900 km/h (515–560 mph) at typical cruising heights.
What is a Mach number?
At high altitude, airliner speed is usually described as a Mach number — the aircraft’s speed as a fraction of the speed of sound.
- Mach 0.85 means 85% of the speed of sound
- Mach 1.0 would be the speed of sound itself
The speed of sound isn’t fixed — it falls in colder air, and it’s much colder up at cruising altitude than on the ground. That’s why pilots track Mach number rather than a plain speed once they’re high up: it’s the number that matters for how the air flows over the wings.
Why don’t jets just fly faster?
Airliners cruise close to — but deliberately below — the speed of sound. Push much faster and shockwaves start forming over the wing, which sharply increases drag and fuel burn. So each aircraft has a sweet spot: fast enough to keep flights short, slow enough to stay efficient.
Flying supersonic is possible (Concorde did it), but the fuel cost and noise make it impractical for ordinary passenger service.
Airspeed vs. ground speed
Two different “speeds” often get confused:
- Airspeed — how fast the aircraft moves through the air around it.
- Ground speed — how fast it moves over the ground below.
A strong tailwind can push ground speed well above airspeed. This is why an aircraft riding the jet stream eastbound can show a ground speed over 1,000 km/h on a tracker, even though it’s cruising at a normal Mach number through the air.
What you’ll see on the radar
The speed shown on the FlyOverhead radar is ground speed. A jet at cruise usually reads somewhere around 800–950 km/h; a much lower number means it’s climbing, descending, or on approach.