DHC-6 (UV-18B) Twin OtterUV 18 Otter USAF Academy airplane model. The UV 18A 'Twin Otter' is the military version of the DeHavilland DHC 6 with optional float and ski fittings. The aircraft have crew and passenger oxygen systems and a navigation communication package which gives it an all weather capability. It has a cruise speed of 150 knots, a service ceiling of 25,000 feet and a range of 700 miles. Designed to replace DHC 3, DHC 6 made its first flight on May 20, 1965.