This is the Boeing 307 Stratoliner:
"The maiden flight of the first Boeing 307 Stratoliner (not a prototype, as it was planned to be delivered to Pan Am following testing and certification), registration NX 19901 took place from Boeing Field, Seattle on December 31, 1938.[8]
This aircraft crashed on March 18, 1939, while being demonstrated to representatives of KLM. After takeoff the aircraft climbed to an altitude of 11,000 feet. At this altitude, longitudinal stability tests were made. The next tests, as outlined by the flight plan, were side-slip tests. The aircraft went into an inadvertent spin subsequent to a stall at an altitude of approximately 11,000 feet. It made two to three turns in the spin, during which the engines were used to aid recovery. In recovering from the dive subsequent to the spin, the wings and horizontal tail surfaces failed upward apparently due to air loads in excess of those for which the aircraft was designed. The ten people aboard, including the KLM technical director, a representative of the Dutch Air Ministry, a Boeing test pilot, the Boeing Chief Aerodynamicist, the Boeing Chief Engineer, and a TWA representative were killed.[9][10] Subsequent wind tunnel testing showed that the addition of an extended dorsal fin ahead of and attached to the vertical tail prevented rudder lock. The redesigned vertical tail and fin were tested on NC 19903.[11] This was incorporated into the 307's rudder redesign, while also being incorporated in Boeing's rear fuselage redesign for their models "E" through "G" B-17 bomber."
Don't see how it could get any worse. And what does it mean for wings to fail upward?