I fly with a pal most of the time, not always in the air together, but regularly we have 2 drones in the air. It can take a little thought and planning, mostly during take off and landing, but also altitude as we move about. In the early days we did a lot of training, comparison tests of props, batteries and other kit using identical drones. We did find my drone drills, landing on a pre set mat at distance and using drone 2 to find drone 1, for emergencies, as well as using the find my drone in the app. Much of the reason for the training is to allow continious monitoring of wildlife over periods longer than a battery can allow, so we can have a drone leave the subject as the 2nd one is arriving, and so suits our needs well. We have also had drone filming subject, being filmed by another drone, and this took a fair bit of practice, as seeing a drone in the air with another drone is tricky, they are really not easy to see up there at times. It took a lot of height planning and discussion, and tought us a lot about the wind currents they can throw out, as an example, you really dont want a mini any place near an inspire in flight!