United Airlines' announcement that it plans to buy 15 supersonic aircraft from the startup Boom Supersonic is raising questions about the future of ultra-fast plane travel. In this video, WSJ speaks with an industry analyst to better understand what’s next for faster-than-sound air travel. Photo: Boom Supersonic More from the Wall Street Journal: Visit WSJ.com: http://www.wsj.com/ Visit the WSJ Video Center: https://wsj.com/video On Facebook: https://www.facebook.com/pg/wsj/videos/ On Twitter: https://twitter.com/WSJ On Snapchat: https://on.wsj.com/2ratjSM #WSJ #United #BoomSupersonic