Thanks to a bloody big rocket - and of course the all moving tail-plane - wherever that was designed!
Interestingly enough, the 'all moving tail-plane' was not incorporated into the F-86 until the D model. The XP-86 that Welch was flying had a fixed tail-plane. Never the less, the F-86, even the D series, had to be in a dive to exceed Mach 1.