Accelerating the human body to mach 20 has its own set of problems. Namely, the g-force involved. A mach number is dependent upon altitude, but they mention 13,000 MPH in the article. This is a little bit slower than the orbital velocity of the Space Shuttle (around 18,000 mph), but at these speeds, rocket launches are the neighborhood we're operating in.
Wikipedia says Shuttle astronauts experience around 3 Gs. This isn't intolerable, but g-force tolerance is heavily related to time spent at a specific level. Astronauts are screened for tolerance to g-forces as part of their selection criteria. It is unlikely that the general public would ever ride in aircraft that subject passengers to the forces commonly felt during the launch of an orbital vehicle.
Wikipedia says Shuttle astronauts experience around 3 Gs. This isn't intolerable, but g-force tolerance is heavily related to time spent at a specific level. Astronauts are screened for tolerance to g-forces as part of their selection criteria. It is unlikely that the general public would ever ride in aircraft that subject passengers to the forces commonly felt during the launch of an orbital vehicle.