Why do commercial air planes cruise at 30,000 feet?



  1. 0 Votes

    The cruising altitude of any airplane (especially commercial) is simply a proliferation of the OPTIMAL height above sea level based on weight.  On longer flights, as airplanes use up more fuel, they become much lighter – a lighter airplane has a higher optimal cruising altitude, where a heavier plane’s optimal altitude is lower.  Most commercial airlines have fleets of planes that all weigh about the same, thus their optimal cruising altitude is typically the same – thirty thousand feet, or “flight level 300”.

  2. 0 Votes
    The reason why commercial planes fly at 30,000 ft is basically because the air is thinner, so the aircraft has to push less out of the way to fly the same speed at a lower altitude where the air is more dense. This concept is called “cruising”.  Another reason is because the winds are much much faster, especially in the jet-stream, and a good pilot can use the winds to his advantage in a tail wind and fly faster and farther with less fuel.  If there is a strong headwind, a pilot can avoid the disadvantage of headwinds as much as possible by varying his altitude accordingly.  Also, heavy turbulence is avoided where rising warm air meets cool air (typically below 30,000 ft).
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