Cruise (aeronautics)

Factors affecting optimum cruise speed and altitude include payload, center of gravity, air temperature, and humidity.

[9] However, LRC speed does not take account of winds, or time-related costs other than fuel, so it has little practical value.

[12] In the presence of a tailwind, LRC speed may give a higher fuel burn than ECON.

[13] Combustion engines have an optimum efficiency level for fuel consumption and power output.

[14][better source needed] Generally, gasoline piston engines are most efficient between idle speed and 30% short of full throttle.

For traffic control reasons it is usually necessary for an aircraft to stay at a cleared flight level.