Lidar's range is measured in hundreds of meters. That might be a bit limiting for flight. Radar could be used, but you might not want to have a "hey all, I'm he

Lidar's range is measured in hundreds of meters. That might be a bit limiting for flight. Radar could be used, but you might not want to have a "hey all, I'm here!"-beacon for military purposes. You could of course use cameras, pointing either up (stellar navigation) or down, but that's not going to work all the time.