Airspeed and Groundspeed

An aircraft’s speed is measured in a vari­ety of different ways. Its speed across the ground is called its groundspeed. An airplane’s speed compared to the air through which it moves is called its true airspeed. If the air is moving (if there is a wind blowing), the groundspeed and true air­speed are not the same. The speed that appears on the airspeed instrument in an aircraft’s cockpit is the indicated airspeed. Pilots used to do complicated cal­culations to convert the indicated airspeed to the groundspeed, which is the speed the pilot needs to know for accu­rate navigation. Today, flight computers and electronic navigation systems take care of this task.