Some years ago there was discussion about somebody designing a Bell X-2. Though it had a short lived history because they were all destroyed, the Bell X-2 still was the first aircraft to fly over 100,000 feet and the first to fly faster than Mach 3. There are models of the X-1 (Mach 1), D-558-II (Mach 2) and X-15 (Mach 4, 5...) so I really need to fill in gap with the historic X-2.