![](https://www.historynet.com/wp-content/uploads/2017/10/Super-D-558-960_640.jpg)
The Douglas D-558-1 took a more conservative approach to supersonic flight research with its thicker wing section, turbojet engine and landing gear. (National Archives)
The Douglas D-558-1 took a more conservative approach to supersonic flight research with its thicker wing section, turbojet engine and landing gear. (National Archives)