Hypersonic and supersonic civilian transport. SpaceX published a first render of what parabolic arcs through low-earth orbit would look like. With estimated one-way arrival time under an hour. YC's own Boom Aerospace is set to announce first flight of its experimental XB-1 aircraft sometime next year. But it is just the beginning. Latent consumer demand could equal 100M+ passengers per annum. The technology is here today. It's simply not evenly distributed yet ;)