Did you know there are "ghost signals" stuck in the ionosphere from years and years ago, bouncing around until they finally lose all their power? Pilots and radio operators as recent the first Iraq war claimed to sometimes hear radios signals from WWII and Vietnam. We used such high power transmitters that apparently you can sometimes pick up and old signal that has just been stuck in the atmosphere since then.

We used to have over-the-horizon communications that utilized atmospheric propagation, they bounced radio waves off the atmosphere over mountains for communications prior to having the networks and communications we have now. There were notable US over the horizon transmitters in Italy but they are abandoned now.