Question
: What is the baseline for altitude while flying? When they say it is 30,000 feet, is it from the altitude of the origin or destination or something else? It can't be the terrain that the plane is flying over, as it would constantly change. Thanks!- Mihika -
Answer : The baseline is what is known as Mean Sea Level or MSL. When a pilot sets an altimeter it reads feet above sea level. In that way, everyone is operating on the same level. The altitude above the ground or AGL is the actual height above the Earth an airplane is flying. You are correct that if we only used the AGL setting, airplanes would be flying at different altitudes. By using sea level as the baseline, all aircraft are flying at the same height. If you wish to learn more about the subject you can go to the “Federal Aviation Regulations/Aeronautical Information Manual” (FAR/AIM), which any airport near you will have. This information is found in Section 2 “Altitude Setting Procedures” beginning on page 840 of the Aeronautical Information Manual. Hope this helps you understand...the procedures taken are to insure all the aircraft in a given area are following the proper safety precautions. Joel Godston
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