Originally Posted by
Biscuit
One of the biggest hurdles with supersonic passenger planes is the sound. I don't know if you have ever heard the sonic boom but they can genuinely be heard across entire counties. This means you need a plane that's capable of flying both sub (for above residential areas) and supersonic for reasonably long distances.
If they could develop an upgrade path that fits within the existing limitations of the transport systems, I think more people would step up and take notice.