Why Am I Not Flying on a Supersonic Jet?

Sitting out a flight delay in a congested airport terminal can inspire some Walter Mitty-style dreaming about a better way to travel. It’s fair to wonder why we don’t fly any faster now than six decades ago, when the Boeing Co. 707 was the pinnacle of aviation technology. From 1976 to 2003, deep-pocketed passengers could fly the Atlantic at twice the speed of sound on a Concorde. But costs and noise complaints killed off that first supersonic jet. Now NASA, Lockheed Martin Corp., General Electric Co. and a number of startups see new designs and technology that could make supersonic flight a commercial reality.

All of the supersonic aircraft projects under development will break Mach 1, or the speed of sound, which at sea level is about 760 miles per hour (1,223 kilometers per hour). The slowest aircraft under development plans to cruise at Mach 1.5 while the speediest will zip along at Mach 2.2. Back in the day, the Concorde would jet across the Atlantic at around Mach 2, connecting New York and London in about 3 1/2 hours--around half the time of a subsonic flight.