I don't know where you have got the info from about below 12k. But it's wrong! An F16 (or any other fast jet for that matter) can not do the job as well as a Hog. For a start it can't fly as slow so can't operate as low nor is it built to withstand as much as the A10. An F16's only use for CAS is to drop ordnance or conduct a SoF. It can't do strafing runs anywhere near as effectively (it can do them but not as precise or as intense). It was tried to be killed off because of the expense of keeping it going and the cost of developing a new version. They are currently keeping it in service as the need for CAS will remain, even in a modern battlefield. It is also very useful in COIN ops as the Gun is the easiest to achieve a 0/0 CDE vs Brimstone or any other bomb. They are however looking at a replacement and they are looking at employing the same design idea. I.E build the plane around the gun. Anyway we are waaaaay off topic now. Planes, Helo's and Ships don't have to worry about headlights in Europe.