Plain English Meaning

EFAS was a dedicated radio service pilots used in flight to get up-to-date weather along their route. It is no longer in operation, but the same kind of weather help is now provided through regular Flight Service.

Full Definition

A discontinued Flight Service radio service, formerly available on 122.0 MHz below 18,000 feet, that provided pilots already in flight with real-time weather information tailored to their route, altitude, and aircraft type. EFAS, commonly called Flight Watch, was retired by the FAA in 2015, and its functions were absorbed into standard Flight Service frequencies.

Context Anchor

Seen in discussions of in-flight weather services, especially near HIWAS and other hazardous-weather advisory material.