What was the original designation of the first aircraft to break the sound barrier?

The first aircraft to break the sound barrier was originally designated as the XS-1. This aircraft, which is more commonly known as the Bell X-1, was developed specifically for high-speed flight research. The XS-1 designation was part of the U.S. Army Air Forces' early research program in the late 1940s and reflected its experimental and high-speed mission profile.

On October 14, 1947, piloted by Chuck Yeager, the XS-1 achieved a speed greater than Mach 1, marking a significant milestone in aviation history. Understanding this distinction in designation emphasizes the importance of accurate nomenclature within the context of experimental aircraft and the historical advancements in aeronautics. The X-1's success paved the way for further developments in supersonic flight and supersonic aircraft design.