transition level

transition level (usually uncountable, plural transition levels)

1. (aviation) The lowest flight level above the transition altitude; depends on the transition altitude and the measured or calculated sea-level atmospheric pressure. The flight level at which a descending aircraft's barometric altimeters are reset from a constant setting of 1013.25 hectopascals to the setting corresponding to the actual measured or calculated atmospheric pressure at mean sea level.

• transition altitude

• transition layer