Douglas DC-7 Delta AirlinesDouglas DC 7 Delta Airlines airplane model. The DC 7 was the last of the Douglas propeller powered transports. Introduced in May 1953, it entered service with American Airlines in November 1953. It was the first commercial transport able to fly nonstop westbound across the United States against the prevailing winds. Douglas built 338 DC 7s and delivered the last in 1958. Most DC 7s were modified as freighters or scrapped. Some were kept for air