At FL350, for example, the air is considerably thinner than at ground level. How do jet engines efficiently provide thrust when considering fuel consumption for a certain throttle setting?

  • $\begingroup$ By compressing the air, also note that because the air is thinner, drag on the airframe is reduced. $\endgroup$ – Ron Beyer Jan 10 '17 at 21:41
  • $\begingroup$ Isn't there less air to compress for any unit time though? $\endgroup$ – flextempers Jan 10 '17 at 21:42
  • $\begingroup$ Related, possibly duplicate: Why are many jet aircraft designed to cruise around FL350-370? or Why do jet engines get better fuel efficiency at high altitudes? (linked to previous one). $\endgroup$ – mins Jan 10 '17 at 21:45
  • $\begingroup$ Yes, but the engines take in a lot of air... I'm a little confused by your question though, are you under the impression that a throttle setting directly translates to a particular rated thrust output regardless of altitude? $\endgroup$ – Ron Beyer Jan 10 '17 at 21:45
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    $\begingroup$ Yes, thrust decreases, but it isn't dumping in the same amount of fuel based on throttle settings either. There is an air/fuel ratio that needs to be maintained for optimum burn. It isn't like a mechanical linkage between the fuel valve body and the throttle handle, there is a system in there to regulate fuel (and other things). $\endgroup$ – Ron Beyer Jan 10 '17 at 22:11