Automatic Terminal Information Systems

Message Format

Every ATIS message includes the same key components, which are presented below in the same descending order.

The first item in any ATIS message is the airport or facility name followed by a letter designation that serves to identify the specific version of the message. Letters are assigned in order, progressing through the alphabet from A to Z with each update. The letter is used to confirm that the pilot is referencing the latest information during correspondence with air traffic control.

[Page 185]The time of recording is given next and is presented as Greenwich Mean Time, regardless of the airport or pilot's location. Recordings are typically made 10 minutes to 15 minutes before each hour. There is a slight delay before the recording is available via ATIS so there may be a very small window of less than two minutes when no ATIS information is heard.

The third item on each recording addresses winds. Winds can be listed descriptively using words like “calm” in conjunction with details about direction or they may be given as a combination of direction and speed. Wind direction indicates the magnetic direction from which the winds originate. The information makes it convenient for pilots to compare wind direction with the runway in use to determine headwind. Wind direction may also be listed descriptively as “variable” or as being variable between two directions. Wind speed is provided in knots and may be presented as a specific number alone or as a number gusting to another number.

Visibility is the fourth item covered in ATIS recordings. It is most commonly given in terms of statute miles (1,609 meters = 1 statute mile) versus nautical miles (1,852 meters). Many locations report any visibility greater than 10 statute miles simply as “10sm.” Anything that negatively affects visibility, such as mist, haze, or smoke, is also reported. Since visibility has the potential to vary greatly depending on direction of viewing and sun interference, any significant variances in visibility would likely be noted as well. Wind direction and velocity must be reported from certified direct-reading instruments.

The next topic covered on the ATIS message is clouds. Because clouds occur in multiple layers, the message is reported from the lowest layer to the highest, using feet above ground level. The type of cloud base is also reported, such as “broken” or “scattered.” If the cloud coverage is less than one-eighth of the visible sky, the cloud section of the ATIS message may simply indicate “clear.” The cloud ceiling—above which aircraft may be unable to climb—is indicated by the lowest cloud level assessed as being either broken or overcast. Many ATIS systems use automated sensors to determine cloud status. Any indications of lightning, dense clouds signaling storm activity, and unstable convection clouds must be reported via ATIS.

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