In the 1940s, the British aircraft designer John Carver Meadows Frost developed the tailless jet-powered research aircraft called the de Havilland DH.108 Swallow, built using the forward fuselage of the de Havilland Vampire jet fighter. One of these was possibly one of the first aircraft ever to break the sound barrier - it did so during a shallow dive, and the sonic boom was heard by several witnesses. [citation needed] All three built were lost in fatal crashes.