b40

The first Boeing Model 40.

Modified Model 40.

This is a (relatively rare) photo of the original Boeing Model 40 powered by a (by 1925, heavy and inefficient) Liberty Engine - as specified by the US government, which had hundreds of surplus Liberty L-12 engines from World War I production. The aircraft was designed and built to compete for US Post Office Air Mail service contract for 50 aircraft. Ultimately, the Douglas M-2 would get the contract. However, an improved Boeing Model 40, the Boeing Model 40A, would provide the impetus for the development and production of the Pratt & Whitney Wasp radial engine, as well as representing Boeing's start in building airliners. See: www.avsim.com/pages/0809/GAS/B40.htm en.wikipedia.org/wiki/Boeing_Model_40

Nice photo, but there are some problems with the Smithsonian's description and dating. There are no DH-4Bs in this photo; most of the aircraft shown are Douglas, not just the ones on the left. They all share the Douglas's distinctive vertical fin shape, quite different from the DH-4B's, and they are "single-bay" biplanes with one set of interwing struts per side; the DH-4B was a "twin-bay" biplane with two sets of interwing struts on each side. Also, the Douglas planes must be either M-3s or M-4s; the M-2 was only bought by Western Air Express, not by the Post Office. The Boeing 40 belonged to Boeing Air Transport, judging by the logo on the side. (Going by the tail number, it appears to be the one registered as NC285.) These details mean the photo must be a few years later than 1924, because at that time the Douglas and Boeing planes didn't exist. 1927 seems most likely: the Boeing 40 had entered service, but the U.S. Post Office hadn't yet stopped flying the mail itself.

Thank you, Colin! You are correct and we will redo the caption shortly.