There has been a renewed interest globally in civil supersonic overland flight that has fostered numerous research and technology development activities. It is now possible to design a low-boom aircraft with a carefully tailored vehicle shape that controls the far field pressures and minimizes sonic booms on the ground. This section will describe recent international advances and cooperative research in sonic boom design, propagation modeling, and human subjective response in preparation of potential international rule changes that will permit civil supersonic flight over land.