What is FSS? FSS or Flight Service Station Is an Air Traffic Service unit operated by Flight Service Specialists that provide Aerodrome Advisory Services. FSS units in Canadian charts are depicted by HEAVY LINE BOXES with the corresponding frequency at the top of the HEAVY LINE BOX, and their call sign is the (unit name) RADIO. Flight Service Specialists assist in maintaining aviation safety, pertinent to the arrival and departure phases of flight at uncontrolled aerodromes and for transiting th