Definition
A ground-based service that uses Mode S radar data to send nearby traffic information up to a properly equipped aircraft, displaying surrounding traffic on a cockpit screen along with relative altitude, direction of travel, and approximate position. TIS is provided only within the coverage of certain terminal Mode S radar sites and requires a Mode S transponder with TIS capability and a compatible display.
Plain English
A service that takes what radar already sees on the ground and beams it up to your aircraft, so you can see other planes around you on a screen in the cockpit.
Context Anchor
Seen in discussions of cockpit traffic displays, instrument flying safety systems, and traffic advisory equipment.
Why Pilots Care
Provides real-time awareness of nearby traffic to help prevent mid-air collisions, especially when visibility is limited.
Analogy
Like having a ground controller send you a simple map of other cars on the road ahead so you know where to look.
Intuition Check
Do not read “traffic information” as a complete picture of all aircraft around you. TIS can improve awareness, but it is not a guarantee that every nearby aircraft is shown.
Example Sentence 1
Before departure, the pilot confirmed the Mode S transponder was set up correctly so TIS traffic would appear on the cockpit display.
Example Sentence 2
During the IFR descent, TIS helped the crew maintain separation from an aircraft not visible outside the cockpit.