Only ten Stratoliners were built: three for Pan Am; five served with TWA; and a ninth Stratoliner was supplied to Howard Hughes. The prototype Boeing 307, NX 19901, crashed during a test flight.  For its part, TWA put it into service on the transcontinental route on 8 July 1940, reducing travel time to 13 hrs. 40 min.  This is an unused, official TWA card.  Grade: 1