The US aviation regulator, the FAA, is considering a shift from speed-based limits set in 1973 to new noise-focused regulations, potentially clearing the way for supersonic passenger jets to return. These aircraft, which travel beyond the speed of sound, have the potential to reduce flight durations by as much as 50%. Back in 1973, overland flights were restricted due to worries regarding the sonic boom, a loud, thunderous noise that impacts the ground.