Swarms of unmanned aerial vehicles (UAVs) are used in search and rescue, infrastructure inspection, and environmental monitoring. An operator supervising such a swarm has to follow many vehicles at once, understand where they are relative to one another, and issue commands to groups rather than to single drones. Ground control stations present this three-dimensional situation on flat screens, which leaves the operator to reconstruct the spatial picture mentally. A Mixed Reality (MR) headset can instead place drone positions, planned trajectories, and status information in the space where the drones actually fly.