So far, the United States has had to worry about losing UAVs to enemy ground fire. But in one recent case, a U.S. UAV was shot down by an Iraqi fighter aircraft. While shot down UAVs don't endanger the lives of pilots, the pilotless aircraft are still expensive. And if you lose enough UAVs, you no longer have a sufficient number left to do the job. So UAV designers are looking at ways to make the aircraft more secure from ground or air attack. This won't be easy, because the most lethal weapon against UAVs is machine-guns on the ground. If the UAVs fly high enough to get away from the light and heavy machine-guns, then they have to worry about missiles. One likely solution is to equip UAVs with the new, cheaper and lightweight "missile detectors" and similar sensors that will notice when machine-gun fire from the ground is getting close (a form of motion detector does this.) Once the UAV detects that it is under attack, there are a large number of rapid maneuvers the UAV can take to avoid the fire. These maneuvers are well known, having been invented over the last century by pilots successful in using them to avoid attack. The challenge is to develop software that will automatically recognize situations and take evasive action. And UAVs can perform these maneuvers more violently because they do not have a pilot on board who would black out if the rapid turns went as far and fast as the aircraft allowed. While these additional sensors will add weight, the growing losses of UAVs to ground fire is making any kind of solution cost effective.