The Boeing design team, headed by Jack Kylstra, initially intended the aircraft to use Allison V-3420 liquid-cooled W engines; since these were not ready, Pratt & Whitney R-1830 air-cooled radial engines were used instead [REF].
Starting in August 1934, Boeing began designing the Model 299 in answer to a proposal by the USAAC to replace the Martin B-10 bomber.