The correct record is: Charles Yeager was the first to exceed the speed of sound in level flight, in the X-1.
This X-1A was flown between Feb 1953 and Aug 1955. Chuck Yeager made four (4) of the 26 flights this aircraft made. Arthur Murray was the primary pilot with 14 flights.
I believe Bob is right , there was no expectation for George to break to Mach 1 , it just happened , Chuck get credt though for the planned flight , both were extremely courageous pilots.
I believe George Welch broke it first (intentionally) in an F-86 Sabre whilst in a shallow dive a couple of days before Chucks official record.
Chuck was the first in straight and level flight
Nope, this was an updated model of the plane that broke the sound barrier. That plane was simply designated the X-1, flown by Chuck Yeager and the sound barrier was broken in Oct, 1947.