DHC-6 Twin Otter floatDHC 6 Twin Otter airplane model. Development of the Twin Otter dates back to January 1964 when De Havilland Canada started design work on a new STOL twin turboprop commuter airliner (seating between 13 and 18) and utility transport. The new aircraft was designated the DHC 6 and prototype construction began in November that year, resulting in the type's first flight on May 20 1965. After receiving certification in mid 1966, the first Twin Otter entered