This was in a FAF game played offline, but I have the replay available.
I had 2-3
T2 Fighter Bombers (Notha's) on patrol. They repeatedly flew over an enemy T3 MEX and didn't attack it.
This happens around 38:00 in the replay, bottom left corner of the map.
Replay attached. There was a DilliDalli AI in the game, if that matters.
All fighter-bombers ignore (sometimes they don't) ground targets unless ordered to attack a specific target
Ah! I didn't realize that. Thanks for the response!
In the same replay, the Notha's attacked ground units, completely on their own, without any orders, so I was expecting the same here. They weren't on a Patrol order at that time, so obviously Patrol works differently. They act as Fighters-only when on Patrol.