Keystone Aircraft Corp
Originally Huff-Daland; became Keystone March 1927, still centered at Bristol, Pennsylvania.
The XLB-1 three-seat, single-engine light bomber was tested in 1923 and was developed as the twin-engined XLB-3, with a crew of five. In 1924 Huff-Daland was reorganized as Keystone Aircraft Corporation and the production bomber aircraft was known by this latter company name.
Keystone was main supplier of twin-engined bombers to U.S. Army from 1927 to 1932, when James McDonnell (later of the McDonnell Douglas Company) was chief engineer. LB- 5A (25 delivered in 1928) was first true Keystone bomber. Largest USAAC bomber order in a decade was for 63 LB- 10A (all converted to B-3A and B-5A on change of Army categories).
Last production contracts for bombers placed 1931 (for 25 B-4A and 39 B-6A).
Keystone Aircraft Corporation built a total of 220 aircraft in the US Army Air Corps LB (light bombardment) category, venturing briefly also into the B (bombardment) and HB (heavy bombardment) classifications. All except ten of the LBs were twin-engined aircraft, but had their origins in the single-engined XLB-1 prototype and nine pre-series LB-1 biplanes produced in 1925 by Key-stone's predecessor company, Huff-Daland and Co Inc of Ogdensburg, New York, which became Keystone in March 1927.
Pathfinder was three-engined civil transport; NK a biplane trainer for a 1928 competition (19 built); PK a twin-engined flying-boat based on NAF design (18 delivered in 1931). Patrician was three-engined 20-passenger low-wing monoplane.
Later absorbed Loening, becoming Keystone-Loening, and then became part of Curtiss-Wright.
Other types were characteristically Loening, including the OL-8 biplane amphibian; the Air Yacht civil amphibian; and the Commuter four-seat cabin amphibian.