Why do pilots no longer wear flak jackets? While U.S. ground troops have been using body armor for some 50 years (since the Korean war), the first use was during World War II, when the first widespread use of body armor in modern combat occurred. Back then, the armor was used in heavy bombers, after it was observed that most of the deaths and injuries were from relatively low velocity shell fragments. The results of using the flak jackets (and other bits of armor, like underneath and behind seats) were dramatic when some crews were equipped with the equipment. During the study period, bomber crews (of the same type of aircraft and missions) without armor suffered 35 percent dead and 65 percent injured (and out of action until their wounds healed) among those who were hit during missions. But the crews wearing flak jackets, which suffered the same number of men hit, had only 21 percent killed, and only 16 percent injured. Thats a total of only 37 percent who became casualties after being hit by shell fragments, versus 100 percent for those not using the equipment. Moreover, 62 percent of the airmen with flak jackets when hit by fragments were able to immediately return to duty, versus none of the crews without flak jackets. Bomber crews were, if anything, more exposed to enemy fire than the infantry. In the air, metal fragments from exploding anti-aircraft shells, or machine-gun bullets from enemy fighters, could come from any direction. You could not dig a foxhole in the air. The air force flak jacket, made up of many layers of nylon, was too bulky and heavy for use by ground troops. Even the air crews didn't put the things on until they were approaching the "flak zone" (concentrations of enemy anti-aircraft guns.) As uncomfortable as they were in their flak jackets, the airmen quickly noticed the advantage of using them. But U.S. aircrew no longer wear flak jackets. It not that they are no longer facing enemy fire, but this happens so infrequently that modern pilots forego the additional protection of a flak jackets in return for being more comfortable while doing their job in the air. The long flights that are so common these days, put a premium on avoiding anything that creates stress, which leads to fatigue, which ends up in making mistakes, often fatal mistakes. Meanwhile, research on lighter flak jackets, that provided better protection continued for sixty years. This resulted in equipment light enough, and providing sufficient protection, to cause ground troops to embrace the use of body armor. It's unlikely that flak jackets will disappear on the ground, as they did on the air. Ground warfare has always been more complex and "busy" than what goes on in the air, and more objects flying around with "to whom it may concern" written all over them.