The Model 40 was Boeing's first passenger aircraft. Two pax sat in the forward cabin and up to 2500 lbs of U.S. Mail was carried. C.A.M.18 was from San Francisco to Chicago - as marked on the "Arrow" insignia. This aircraft was built as a 40A with a 420 hp P&W Wasp, but was converted to a 40B by replacing the engine with a 525 hp P&W Hornet. This gave the 40B a cruise of 110 mph over 550 miles. Obtained from UAL 60 years ago.