Definition
A dedicated in-flight radio service, historically known as Flight Watch, that provided pilots with timely weather information pertinent to their route of flight, altitude, and aircraft type. EFAS specialists also collected pilot weather reports (PIREPs) to update the national weather picture. The service operated on the common frequency 122.0 MHz below 18,000 feet MSL, with discrete frequencies above. EFAS was discontinued by the FAA in 2015, with its functions absorbed into standard Flight Service.
Plain English
EFAS was a radio service pilots could call from the cockpit to get up-to-date weather along their route. They tuned 122.0 and asked a weather briefer for the latest conditions. The service no longer exists by that name, but pilots still find it referenced in older FAA materials.
Context Anchor
Seen in instrument flight planning and in-flight weather discussions, especially when a pilot needs updated weather information after departure.
Derivation
"En route" comes from French, meaning "on the way." "Advisory" signals that the information is offered to help the pilot decide, not to issue instructions. Together: a service offering weather guidance while the pilot is on the way.
Why Pilots Care
Gives pilots immediate access to changing weather data so they can adjust plans before conditions become hazardous.
Intuition Check
Do not read “advisory” as a clearance or command. EFAS gives weather information and advice; the pilot still makes the flight decision and must follow any required air traffic control instructions.
Example Sentence 1
The older textbook instructed the student to contact EFAS on 122.0 to request updated weather along the route.
Example Sentence 2
EFAS advised of building thunderstorms and suggested an alternate airport.