Low-wing, all-metal, twin-engine monoplane originally intended as a 6-8 passenger executive or feeder airline transport; 32 different versions produced during production run of over 30 years. Initial acceptance in US minimal, but proved popular in foreign markets. Could be equipped with floats or skis and was popular in Canada and far north. Jan 39, USAAC ordered photorecon version designated Type F-2. Later ordered in other versions as transport, navigation trainer, and bombing-gunnery trainer. Similar versions ordered by USN along with radio-controlled target or drone aircraft. After end of WWII, Beech went back into full commercial production with improved model, D-18S. Prototype of last model to be produced, Super 18, flew 10 Dec 53. In 1970, over 2,000 still being flown.
Had unusually long production run of over 30 yrs (only Beechcraft Bonanza has had longer run); remained in use by commercial operators until well into 70s.