Terminal Radar Service Area

In United States aviation, a Terminal Radar Service Area (TRSA) is a delimited airspace in which radar and air traffic control services are made available to pilots flying under instrument flight rules or (optionally) visual flight rules for the purposes of maintaining aircraft separation.

TRSAs are most often encountered surrounding busy U.S. airports. In recent years many of them have gradually been replaced by Class B or Class C airspace.

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