The DC-3 was a descendant of the DC-1 and was TWA's answer to United's Boeing 247. The DC-1 incorporated Jack Northrop's multicellular wing construction and light yet powerful engines, and carried 12 passengers in relative comfort. The DC-2 production model that followed has 14 seats. The 21-seat DC-3, later able to accommodate 28 or more passengers, was originally designed as a sleeper - the DST - to carry passengers overnight from New York to Los Angeles. With a full load, it was the first transport airplane that could fly passengers without mail and still make a profit. The DC-3's streamlined, versatile design and strong wing construction made it an exceptional aircraft; at least 400 of these airplanes are still flying today.