Boeing B-17 Flying Fortress Boeing B-17 Flying Fortress The Boeing B-17 Flying Fortress is a four-engined heavy bomber developed in the 1930s for the United States Army Air Corps (USAAC). Competing against Douglas and Martin for a contract to build 200 bombers, the Boeing entry (prototype Model 299/XB-17) outperformed both competitors and exceeded the air corps' performance specifications. Although Boeing lost the contract (to the Douglas B-18 Bolo) because the prototype crashed, the air corps ordered 13 more B-17s for further evaluation. From its introduction in 1938, the B-17 Flying Fortress evolved through numerous design advances, becoming the third-most produced bomber of all time,
American Theater (World War II) other heavy bomber projects were cancelled. During the final months of World War II, Japan had planned to use plague as a biological weapon against U.S. civilians in San Diego, California, during Operation Cherry Blossoms at Night. The plan was set to launch at night on September 22, 1945. However it was shelved after Yoshijiro Umezu, Chief of the Imperial Japanese Army General Staff, rejected it. Additionally Japan surrendered five weeks before the plan had been intended to take place. These false alarms have generally been attributed to military and civilian inexperience with war and poor radars of the era.