For Wednesday, we have the first Boeing 307 Stratoliner, which bridged the gap from the end of the Golden Age to the end of WWII.
Sharing the wings, engines, landing gear, and tail of the B-17C bomber, the Stratoliner received an enlarged circular fuselage and pressurization, a first for its day. The 307 was poised to make major inroads into the airline industry, but the outbreak of WWII saw Stratoliner production shift to the military transport version, which was called the C-75. The aircraft in the top photo, NX19901, was the first Stratoliner every built, but it was not a prototype, as Boeing planned to turn the airliner over to Pan American after testing. During a test flight to pitch the 307 to KLM executives, the aircraft entered a spin and crashed, killing all 10 onboard. The cause of the accident was traced to rudder lock, and subsequent C-75s, and B-17s, were modified by extending a dorsal fin in front of the vertical stabilizer. Only ten 307/C-75s were built, and the sole survivor is kept in flying condition at the Steven F. Udvar-Hazy Center near Washington DC.