In the context of aviation and aerospace, "Airport Advisory Service" refers to a type of air traffic control service provided to aircraft operating at an airport, typically a non-towered airport or an airport with limited air traffic control services.

At a non-towered airport, there is no air traffic control tower to provide separation and sequencing of aircraft. Instead, pilots communicate with each other and with other aircraft in the vicinity using a common frequency, often called the "Common Traffic Advisory Frequency" (CTAF) or "Unicom" frequency.

Airport Advisory Service is a type of advisory service provided by a Flight Service Station (FSS) or a remote air traffic control facility to aircraft operating at a non-towered airport. The service provides pilots with information about:

1. Airport conditions, such as weather, runway conditions, and obstacles.
2. Other aircraft in the vicinity, including their location, altitude, and intentions.
3. Recommended traffic patterns and procedures for arrival and departure.

The Airport Advisory Service is typically provided by a trained air traffic control specialist who has access to radar and other surveillance systems, as well as information from nearby airports and air traffic control facilities. The specialist provides advisory information to pilots, but does not have the authority to issue clearances or instructions.

Pilots use the information provided by the Airport Advisory Service to make informed decisions about their flight operations, such as planning their approach and departure, avoiding conflicts with other aircraft, and navigating the airport environment safely.

It's worth noting that Airport Advisory Service is not a substitute for air traffic control services, and pilots are still responsible for see-and-avoid and following standard operating procedures at non-towered airports.