 The cheaper materials were too heavy, and the Air Force was not happy that Boeing did not meet the Air Force's expectations on the prototype even though the Air Force was aware that they would be using different materials in the production of the actual aircraft.The Apache helicopter that Boeing makes is designed so the front of the helicopter is very narrow.Not only does it create less drag, but it is a smaller target for infantry units to hit the helicopter.They have also designed the F-15 fighter jet, which has two engines instead of one for maximum speed.