Just announced in the press conference as Mach 1.24. Incredible.
But shouldn't we have seen a sonic boom then?
Not necessarily. The reason we can see the sonic boom is because where the air is accelerated past the speed of sound there is a rapid increase in pressure. This is called the shock wave. If there is water vapour present in the air, the rapid increase pressure will cause water droplets to form at the location of the shockwave. Felix was so high when he broke the sound barrier, there was almost no water present so it would have been impossible to see the sonic boom without proper imaging instrumentation.