De Havilland actually made the first ever jet engine aircraft, called the De Havilland Comet, which sparked the jet age. Unfortunately a lot of terrifying midair break-ups happened due to the square windows, which made the Comet unpopular and forgotten. Boeing and McDonnell Douglas took notes about this and soon made the Dc - 8 and the 707.
De Havilland then retired, and turned into De havilland Canda, which made the Dash 8.