Definition
A service provided by air traffic control to pilots flying under Visual Flight Rules in which the controller informs them about other aircraft observed on radar that may be near their flight path. The service is workload-permitting and does not relieve the pilot of the responsibility to see and avoid other traffic.
Plain English
When a pilot is flying by visual reference rather than on an instrument flight plan, ATC can call out other aircraft they see on radar that might be close. It's a heads-up, not a guarantee, and the pilot still has to look out the window for traffic.
Context Anchor
You may encounter this term when talking with ATC during VFR flight following, radar services, or instrument-training discussions that show how controllers sequence and monitor aircraft.
Derivation
“Advisory” comes from “advise,” meaning to give information or counsel. That helps here because a traffic advisory is information to help the pilot make a safe decision; it is not the same as a clearance or a command.
Why Pilots Care
Gives the pilot an early heads-up on traffic that might not yet be visible, reducing the chance of a mid-air collision.
Intuition Check
Do not read “advisory” as “ATC is keeping me separated.” A VFR traffic advisory is a helpful warning about traffic; the VFR pilot is still responsible for seeing and avoiding other aircraft.
Example Sentence 1
Center called out VFR traffic advisories on a Cessna at our two o'clock, three miles, opposite direction.
Example Sentence 2
Even on a clear VFR day, the pilot requested traffic advisories while crossing the busy practice area.