SpaceX just proved that it can send a 14-story rocket booster into space and then land it successfully back on Earth. It is something the company had never managed to do before but is essential if Elon Musk has any hope of dramatically cutting the cost of reaching space.

For its next trick, SpaceX will need to master the mundane: launching, landing, refueling, and promptly launching the same rocket again—just like an airplane.

Musk has used the airplane analogy numerous times. The idea is that one day he will have a fleet of airplane-like boosters that can be used many times, turning single-use rockets like those at United Launch Alliance and Orbital ATK into relics. Achieving that goal, which could also herald quicker launch schedules, could lower costs "probably in excess of a factor of 100," Musk said Monday night on a conference call after the mission. "This is a fundamental step change in technology compared to any other rockets that have ever flown."