At the beginning of Editing for OFP (yea those where the times, way back before Red Hammer, Resistance and Laser Designators *schwelg*), anyhow I tried to make it without a Laserdesignator, where you are a forward air
controller guiding in a Strike on, a few tanks, though that was
a lame objective. Normally you'd say it's an not-moving target which is hard to locate form the Air (otherwise they'd do the
job with a F/A-18 or a A-6, Tornado you name it...).
If its in a Vietnam enviroment I'd say a fairly large supply
"base" hidden in the (deep) woods.
Or for Close Air Support for some Infantry troops, which
happen to be under fire, Infantry can be hard to spot from
above (Mortar, Heavy MG for example...)