So I'm watching a documentary on supersonic flight, and the challenges they describe seem SO daunting that I couldn't help but wonder: Wouldn't it just be easier to fly above (most of) the atmosphere? There must be an altitude where sonic booms no longer reach the ground and wind pressure no longer superheats the surface of the plane. Would this be in the mesosphere? There is still oxygen there, so bringing it along would not be necessary. I'm aware of SpaceShipOne, but with only three people on board, it looks more like a thrill ride then a transportation solution.