On a typical flight, after detaching from the balloon, both World View’s and Zero2infinity’s capsules will descend under a kind of steerable parachute called a parafoil, which, when inflated, acts like a wing. World View tested its parafoil in February in a balloon drop from over 100,000 feet, something that had never been done. There were some differences in how it worked in thinner air, says MacCallum, but “fundamentally, it flew.” He has so much confidence in the controllability of a piloted descent that World View plans to put wheels on its capsule so that it can be landed at a downwind airport, rather than retrieved from wherever it happens to end up. World View’s design imperative for all stages of the flight, according to MacCallum, is simple: “You won’t spill your drink.”