Normally people are impressed with aircraft going higher, faster. And that’s certainly worth getting impressed about. But prepare to be impressed with aircraft going *incredibly* slow…
Someday it will be practical to 3D print structures of incredibly lightness using carbon fiber, with structures decimeters long and hair-thin, while still rigid. With skins of graphene and “rubber bands” made out of… well, I don’t know what, imagine the wondrously impractical ghostlike aircraft that will be built. With equally advanced optics and electronics, such aircraft could have cameras and transmitters. carried aloft by high altitude balloons, they could be released at the edge of space to fly for potentially days, covering hundreds or thousands of miles, their weak signals picked up by ground or space based receivers. I don’t know if cameras and transmitters will be good enough to make them useful intelligence gathering systems, but they are very unlikely to be detected by IR or radar. With their carbon constructions and extreme surface area to volume rations, when they are done they will likely degrade away to almost nothing very quickly.