The Airspace That Was Left Behind

In 1993 the current airspace system that uses the alphabet to designate the different airspace types went into effect, replacing all the previous airspace designations, but one. There was one type of airspace that did not fit into any of the new categories, and it still exits today — the TRSA.

The last remnant of the former airspace system is the TRSA. If you think the airspace system is complicated now, I assure you it was much worse before 1993. Airspace types of all descriptions interlocked, overlapped, and co-existed in a maze of different boundaries, rules and procedures. Back then, we tried to decipher Control Zones, Airport Traffic Areas, Airport Advisory Areas, Aeronautical Advisory Areas, Terminal Control Areas, Stage III Radar Area, and Airport Radar Service Areas. All these terms are history now, being replaced with Class A, B, C etc … all except the TRSA.

The original plan was to increase the requirements of the TRSA and turn them into Class C’s. In many places across the country that is exactly what happened. But when the new rules for Class C airspace were established the FAA included a minimum number of ‘operations‘ to qualify. An operation is a takeoff, a landing, or a low approach and some TRSAs simply did not have enough traffic to qualify as a Class C. It was decided that since TRSAs already had all the equipment in place (radar facility, personnel, etc) that they would be allowed to stand as they were — but they are not included in the operating rules of Part 91 (General Operating and Flight Rules).

For pilots, a TRSA is like having a Class D control tower that also has radar capability. Figure 1 shows Monroe, Louisiana, which has one of the last remaining TRSAs. The TRSA symbol is a series of concentric circles printed on the chart in gray. The circles show the extent and altitudes of the TRSA.

» View Figure 1 Chart Example


  • If you are going to land at Monroe, you should call their approach control about 20 to 30 miles out (just like you would at Class C) and get sequenced into the flow of traffic. Eventually the approach controller will hand you off to Monroe Tower for your landing clearance.
  • The inbound-to-land procedure is identical to the Class C procedure.


  • Unlike Class C airspace, a pilot operating inside a TRSA’s circles can do so without communicating with air traffic control. If you were just transitioning through the area — and your flight path would not take you across a Class D circle — then no radio communications would be required.
  • TRSAs do not require aircraft operating in the area to have a Mode-C, altitude reporting, transponder.

Important: Know these differences, but in actual practice communicate with the approach control at a TRSA, even if it is not strictly required. The radar services a TRSA provides (traffic advisories, etc.) can make your flight safer — for you, and other pilots.

Very Important: Look carefully at Figure 1 and you will see a blue-dashed line that overlaps the inner gray circle — it signifies Class D airspace. To enter Class D, you must communicate with the control tower and be granted clearance. Of course, you could fly right up to the inner ring before giving the control tower a call. That is what you could do, but it is not what you should do. A little extra communication — even if you miss an overlapping blue-dashed line — will likely save you from making a costly error.

BOTTOM LINE: Know what the differences are between a TRSA and a Class C — but behave responsibly. As a rule of thumb, treat them like a Class C.