The Keystone XLB-3 (originally built under the Huff-Daland name) was a prototype bomber biplane developed in the United States in the late 1920s. It was a twin-engine development of the single-engine LB-1, brought about by a change in policy by the USAAC.
Read more about Keystone XLB-3: Design and Development, Operational History, Variants, Specifications (XLB-3A), References