Back in the "old days," before radio comms, the U.S. Army and Navy used hot air balloons, some manned, others unmanned (kind of like a paper lantern) with a signals officer and a couple spotters/signalmen and signal flags attached to communicate between separated units. Faster and much safer than sending messengers across exposed fields or trenches.

The Navy used them to communicate with onshore Marine units and the Army when coming to shell a target. The balloons could be floated and seen over treetops and dunes, bldgs, etc. The Navy also used them to signal other ships and to coordinate ship movements from a bird's eyed view.

Back in the "old days" the U.S. Army and Navy used balloons with signal flags attached to communicate between separated units. Faster and much safer than sending messengers across exposed fields or trenches.