The Concorde changed the way we traveled 40 years ago by drastically cutting flight times between Europe and the US. However, the Concorde retired in 2003, and there’s yet to be a reemergence of a commercial supersonic jet. Companies such as Boeing, Lockheed Martin, and Airbus are working towards the next stage of development by reducing the sonic boom, while also keeping in mind efficiency and safety. So, what’s the super holdup with supersonic passenger planes?