Auto GCI is a mechanic that uses your active E2, EWRs and ground units to detect enemy air assets, and update the player with the relative location of enemy aircraft.
The player can get continuous reports (turned on by default) or get a one-time update with the F10 menu F10 -> Targeting -> GCI Report
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The report messages appear as on-screen text and are configurable by the player (see gci).
Once you have been detected, it takes 30 seconds of continuous tracking for VT and 10 seconds for radar track before you are visible by Auto GCI
Tacview shows targets once this time has expired.
Once a unit loses track, it continues to be reported for 12 seconds in the last known position
If track is regained during this period, you are re-detected