It's not just the F-35. The flak future awaiting the F-35 and other U.S. aircraft appears to be a grim one, according to the Air Force. "Legacy AAAs [anti-aircraft artillery] are already lethal to 35,000 feet and will become more lethal as projectiles become smarter and as radar tracking improves. In the near future, they will be more lethal at much higher attitudes as numerous hyper-velocity technologies come online such as railguns and extended range artillery with smart seeker shells come online."