Button depicts a single-wing, twin-engine yellow and white plane and dark blue text over a light blue background.
YANK JUNIOR AIRPLANE SERIES RELIANCE MFG CO CHICAGO ILL.
In the early 1930s, Boeing Company developed bomber aircraft from its existing mail-plane designs. The YB-9 and Y1B-9 were the first all-metal single-wing planes developed for the U.S. Army Air Corps. They featured open cockpits for the pilot and co-pilot, who doubled as the bombardier. Five Y1B-9A test planes were built and entered service in 1932. The more advanced Martin B-10 bomber prototype had already been flown, however, and the last of the Y1B-9As were phased out in 1935.
Boeing developed more advanced bombers such as the four-engine B-17 Flying Fortress and B-29 Superfortress used during World War II. In March 1944, Boeing workers were building 350 planes per month for the war. After the war, Boeing transitioned to building passenger aircraft, including the 747 (1970), 777 (1994), and 787 Dreamliner (2009).