In 1931, the United States Army Air Corps received five working models (Y1B-6s) of the B-6 bomber.The Air Corps placed an order for 39 production models on 28 April 1931, with deliveries between August 1931 and January 1932.[1] At the same time, an order was placed for 25 B-4As, the same aircraft but mounting Pratt & Whitney engines instead of Wright Cyclones.The Douglas Y1B-7 and Fokker XB-8 were originally designed as high-speed reconnaissance aircraft.On December 27, 1935, six B-6 bombers of the 23rd Bomb Squadron based in Hawaii dropped bombs to divert lava flow from the volcano Mauna Loa away from the port of Hilo.