Which Boeing bomber first flew in 1935 as the Model 299 prototype?

The Boeing B-17 Flying Fortress first flew in 1935 as the Model 299 prototype.

The prototype made its first flight on July 28, 1935, from Boeing Field in Seattle. Boeing developed the aircraft for a U.S. Army requirement for a long-range, multi-engine bomber. The Model 299 combined four engines with an all-metal construction and a large defensive armament for its era.

Although the prototype was lost in a 1935 evaluation accident, the Army still ordered production aircraft after Boeing refined the design. The resulting B-17 became one of the best-known American heavy bombers of the Second World War.

The B-17 is sometimes confused with the later B-29 Superfortress, which was a larger, pressurized, long-range bomber. The B-24 Liberator was another contemporary U.S. heavy bomber, but it was designed and built primarily by Consolidated Aircraft, not Boeing.