What aircraft was the first to break the sound barrier?

The X-1 was the first aircraft to successfully break the sound barrier, achieving this milestone on October 14, 1947. Designed specifically for high-speed flight research, the X-1 was a rocket-powered aircraft that demonstrated the ability to exceed the speed of sound in controlled flight conditions. Chuck Yeager, a test pilot, was the one who piloted the X-1 during this historic flight, reaching a speed of Mach 1.06. This achievement was crucial in advancing our understanding of supersonic flight and paved the way for future developments in both military and civilian aviation.

Other aircraft listed, such as the U-2, are known for their high-altitude reconnaissance missions but did not focus on breaking the sound barrier. The Hawker Siddeley 125 is a business jet that operates well below the speed of sound, and the DC-10 is a commercial airliner that was designed for subsonic travel as well. Thus, the X-1 stands out as the pioneering aircraft in supersonic flight history.