Indicated airspeed, or IAS, is the second most important instrument and indicates the airspeed very accurately in the range of 45 to 250 knots.

The True Airspeed (TAS) will be higher than the Indicated airspeed indicated by the Airspeed indicator to the pilot in air of low density.

Maximum operating speed: 400 knots indicated airspeed (KIAS)

He finally realized he was passing three hundred knots indicated airspeed in his F-16, still in zone-five afterburner--and he still had his landing gear down.

Combined with the high airspeed at rotation (199 knots indicated airspeed), this increased the stresses on the rear undercarriage in a way that was initially unexpected during the development and required a major redesign.

Airspace above the United States from the surface to 10,000 feet above sea level is limited to 250 knots (indicated airspeed) per the FAA's Federal Aviation Regulations.

Calibrated airspeed (CAS) is indicated airspeed corrected for instrument errors, position error (due to incorrect pressure at the static port) and installation errors.

Minimum operating speed: 90 knots indicated airspeed (KIAS)

A later modification was added to calculate the difference between true and indicated airspeed, which grows with altitude.

The speeds needed for takeoff are relative to the motion of the air (indicated airspeed).