For impatient travelers, the next wave of air transportation could be a game-changer. Aerospace company Hermeus Corporation recently announced that it has obtained funding to pursue development of a plane that could travel five times faster than the speed of sound, getting passengers from New York to London in just 90 minutes. But it won't be a cheap flight, and the idea isn't without some baggage. The venture, which was founded by former employees of private space travel companies like Elon Musk’s SpaceX and Jeff Bezos’s Blue Origin, is seeking to craft a plane that can travel at Mach 5...