I'm not sure if this is a bug or something strange happening due to objectives, but sometimes in my custom escalation missions, the AI leaves the map border and just flies away from the area, I've seen crickets around 25km from shore, etc.
No clue what's happening, or if it's something that I've set that's messing with the AI. Sometimes the AI flanks, but a lot of the time it seems like they just fly out into the ocean and just loiter.