Last spring, Boeing revealed its proposed hypersonic passenger airliner, which would fly much higher and faster than the Concorde-the only previous supersonic commercial airplane.

For reference, supersonic jets fly over the speed of sound (660 mph or Mach 1), while hypersonics surpass Mach 5 or 3,800 mph.

Boeing told the annual American Institute of Aeronautics and Astronautics conference held in Atlanta that its sleek new airplanes would travel at Mach 5, enabling them to cross the Atlantic Ocean in just two hours and the Pacific in three while cruising at 95,000 feet.

By contrast, the Co...