In response to the loss of the first prototype de Havilland introduced modifications to the design which were implemented on the remaining second prototype. These changes included the adoption of an all-moving tailplane, and cambered leading edge extensions. The modified prototype did not return to flight until July 1954. As a result of these changes the DH 110 was no longer able to exceed the speed of sound, only reaching Mach 0.95 in a steep dive where its controls were immovable until passing . By this time, the Royal Air Force announced the abandonment of its interest in the DH 110, after deciding to buy the Gloster Javelin instead; However, the Fleet Air Arm had decided that it would adopt the aircraft as a replacement for its interim fleet of Sea Venoms. In February 1955, an order was placed for 110 navalised aircraft, which received the name "Sea Vixen".