The Boeing Model 40 was a United States mailplane of the 1920s.
It was a single-engined biplane that was widely used for airmail services in the United States in the 1920s and 1930s, especially by airlines that later became part of United Airlines.
It became the first aircraft built by the Boeing company to carry passengers.
The Honduran Air Force used these as transports.
Variants
Model 40
Original 1925 design with Liberty engine.
Model 40A
Revised 1927 design for BATC, The aircraft was powered by a Pratt & Whitney Wasp radial engine, plus seating for two passengers in an enclosed cabin.
Model 40B
Model 40As re-engined with a 525 hp (391 kW) Pratt & Whitney Hornet radial piston engine.
19 Model 40A were converted.
Redesignated Model 40B-2.
Model 40B-4
Revised Model 40B with seating for four passengers and other improvements.
Equipped with operable windows, plus seating for four passengers.
Model 40B-4A
One Model 40B used as engine test-bed by Pratt & Whitney.
Model 40H-4
Four Model 40B-4s built by Boeing Canada.
Two aircraft were exported to New Zealand.
Model 40C
Similar to Model 40B-4 but with Pratt & Whitney Wasp engine of Model 40A.
(Ten built, all later converted to Model 40B-4 standard).
Model 40X
Unique special-order machine similar to Model 40C with only two-passenger cabin and extra open cockpit forward of pilot’s cockpit.
Model 40Y
Unique special order machine similar to Model 40X, but with Pratt & Whitney Hornet engine.
