The company approached many airlines in order to obtain their requirements for an advanced airliner. No firm orders resulted, although 25 letters of intent were received, sufficient to begin production. The design of a 24–34 passenger airliner proceeded to prototype stage as the CW-20 at the St. Louis, Missouri facility with the initial configuration featuring twin vertical tail surfaces. Powered by two R-2600-C14-BA2 Wright Twin Cyclones, the prototype, registered "NX-19436" flew for the first time on 26 March 1940 with test pilot Edmund T. "Eddie" Allen at the controls. After testing, modifications were instituted, including the fitting of a large single tail to improve stability at low speeds.