The design of the Bell X-1 was started in 1944 and the first prototype was ready in 1946.
The design of the DFS-346 was started in 1944 and the first prototype was ready in 1946.
The Bell X-1 was carried aloft under the fuselage of a modified B-29 bomber.
The DFS-346 was carried aloft under the wing of a modified B-29 bomber. It is thought that the aircraft used was actually a B-29 and not a Soviet Tu-4.
The Bell X-1 broke the sound barrier on 14 October 1947.
The DFS-346 never achieved supersonic flight. The final powered flight in 1951 ended in a crash that destroyed the aircraft.