Especially since they see through terrain objects. I remember doing one missing where I was sneaking into an urban area, low using buildings and hills as cover. When I stopped behind a large hill with some buildings on top. I started hearing explosions coming from a building next to me. I peaked around the corner of the of the building and right there at the bottom of the hill was a sam, pounding the house I was hiding behind.
Another mission I was tasked to destroy some HQ. I decided to flank wide and pop up to find a safe route to target, bypassing all the stuff in between. After scouting for a while, I found an open path through the forest leading all the way to the HQ. I went down below tree top level, following the path to the HQ when suddenly my wingman started shooting flares. I stopped and looked around, no way anyone could see or lock us, or? Suddenly a SAM comes flying out of the forest at my 12 o'clock and flies straight into my cockpit :D