The first modern American bomber was the B-10 of the 1930s. It was an all-metal, twin engine bomber with one defensive turret in the nose. This was followed by the B-18, another all-metal twin engine bomber. These two aircraft were obviously inadequate. A long-range bomber that could carry a heavy bombload was needed. Boeing started working on a four-engined bomber that it called the Model 299. It was a private venture that was tested by the U.S. Amry Air Corps. On the first display flight, the plane crashed, killing all onboard. This could have killed the B-17, but it was decided that the crash was due to human error; the pilot forgot to remove the control lock before take-off. The U.S.A.A.C. accepted the Model 299 and Boeing put it into production. This would be the most important strategic bomber of the war. The Amry Air Force also used other strategic bombers, such as the B-24 and the B-29. Even the enormous six engine (late ten)B-36 was designed for use during World War Two. There was also a large amount of tactical and attack bombers, like the B-26, B-25, A-20, and A-26. The Army Air Force wasn't the only branch of the military that possessed bombers. The Navy used small, single engine dive-bombers and torpedo-bombers to strike targets far at sea. With the ability to strike at the heart of the enemy, America could paralyze any system of transportation and production.