In 1946 The first flight of the four-engine DC-6 commercial transport took place from Douglas Aircraft Company facilities in Santa Monica, California. The DC-6 was the first Douglas airliner with a pressurized cabin. The DC-6 also introduced to airliner service humidity-controlled ground air-conditioning, pre-loaded baggage containers, under-floor baggage compartments, thermal de-icing of wings and tail leading edges, double slotted flaps and reversible propellers. Including its C-118 Liftmaster military transport version, Douglas built 704 DC-6s.