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Old Mar 9, 2017 | 4:14 pm
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WorldLux
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Originally Posted by caliform
Likely IAS - 'Indicated Airspeed', which is not corrected for instrument deviation and added winds. It's not the true airspeed or groundspeed, so in the end you likely weren't traveling at transonic speeds
Depends on what speed is shown. Speed in Mach only really make sense with regard to the altitude. Indications in kph or mph usually refer to groundspeed.

When looking at IAS you need to consider the environment the aircraft is flying in. E.g. Take moving walkways:
  • If you stand on them. Your speed compared to the the moving walkway is 0. Yet your acutal groundspeed is the speed of the moving walkway.
  • If you walk on the moving walkway, you walk walking pace compared to the moving walkway. Your groundspeed is the combination of your walking speed and the speed the moving walkway is operating at.
  • You walk backwards on the walkway at the exact speed the moving walkway is operating. Your ground speed (walking pace + speed of the walkway) is 0.
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