design, ordered in small numbers for National Air Transport. Two were custom-built long-range endurance aircraft similar in concept to Charles Lindbergh's Spirit of St. Louis. Woolaroc, flown by Art Gobel won the disastrous Dole Air Race from Oakland, California to Hawaii in which the majority of contestants disappeared at sea or otherwise died attempting the crossing. Travel Air then produced the Model 6000, a five or six-seat high-wing cabin monoplane — intended for airline use, and for very wealthy private owners. A small fleet of Travel Air 6000s were the first airliners for Delta Air Service (eventually renamed Delta Airlines). In 1928, National Air Transport operated the Type 6000 on their mail and passenger routes from Chicago to Dallas, Kansas City and New York. Two Travel Air 6000 were purchased by the Paraguayan government during the Chaco War (1932–1935) for the Transport Squadron of its Air Arm. These planes belonged to TAT with the registrations NC624K (c/n 6B-2011) and NC9815 (c/n 6B-1029); They received the military serials T-2 and T-5 (later reserialled as T-9). The planes were intensively used during the conflict as air ambulances. They both survived the war and continued flying in the air arm. In 1945, they were transferred to the first Paraguayan airline, Líneas Aéreas de Transporte Nacional (LATN) and received the civil registrations ZP-SEC and ZP-SED. They were withdrawn from use in 1947. Cabin biplanes The CH or 7000 — a single=engine, cabin biplane, with a pilot's open-cockpit above-and-behind the small, enclosed cabin for cargo or passengers — found little success, but ended up in Alaska as an early bushplane. Racing monoplanes Travel Air was also responsible for a series of very successful racing aircraft, which due to the company being extremely secretive about them during development, were named Mystery Ships by the press. In 1929, at the National Air Races in Cleveland, the first Travel Air Model R Mystery Ship became the first American airplane to outrun the nation's top fighter aircraft, winning the Thompson Trophy unlimited-class pylon race. The Mystery Ships dominated the racing circuit for several years and had the distinction of being faster than anything the U.S. military had on strength. It forced the U.S. military to face the need to give up biplane fighters and water-cooled engines. Its renown led to one example being sold to the Italians which inspired the design of a racing aircraft and the Breda Ba.27