Why planes fly at 35,000 feet: The reason for high altitude flights – by Hugh Morris

By chance, we have just discovered this interesting article related to the general cruising altitude of commercial airlines, here is the summery:

  • The “sweet spot” of flying is regarded as between 35,000 and 42,000 feet


  1. Money : heavier planes would fly lower, and lighter higher
    (and provided that the plane has enough power for climbing)
    fly higher thinner air imposes less drag – travel more easily and therefore move faster and burn less fuel, saving money
  2. Range consideration : turbojet engine increases in specific range with altitude.
    • Altitude↑, air den ↓ , TAS ↑
    • OAT ↓ , inlet air temperature ↓  , specific fuel consumption ↓
    • Engine RPM ↑ , specific fuel consumption ↓
  3. WX consideration : Troposphere – that is the atmospheric layer closest to the ground – is home to most of the world’s weather phenomenons. Usually measured up to 36,000 feet. Aircraft prefer life in/near the stratosphere, less WX phenomenons which means less turbulence.
  4. Avoiding Airborne traffic: High also means that aircraft are able to avoid other airborne traffic – e.g general aircraft (GA)/ light planes and helicopter
    (provided that the plane with sufficient O2 supply for Crews and PAX)
  5. In the event of an emergency, pilots have much more time for taking action or related drills
  6. Noise abatement: environmental reasons – planes fly higher, lower noise delivery to the ground

For more details, please refer to the link below:


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