transition area

transition area

Controlled airspace extending upward from 700 ft or more above the surface of the earth when designated in conjunction with an airport for which an approved instrument approach procedure has been prescribed, or from 1200 ft or more above the surface of the earth when designated in conjunction with airway route structures or segments. A transition area usually terminates at the base of the overlying controlled airspace. Transition areas are designated to contain IFR (instrument flight rules).