Brandon lets his mom die because she's not named Martha.
https://www.youtube.com/watch?v=t6UyEPrqaQI
Feat happens at 1:36.
Brandon reaches the stratosphere in 10 seconds.
Since there are clouds, it's not the top of it but the bottom.
10000m / 10s = 1000m/s or Mach 2.9 Supersonic+