but one video account told by Col. Kittinger indicated that he had a small Morse Code Key within reach of his hand, and he transmitted an "OK" message to the ground facility during his assent.
During the great war, British artillery spotters ( the reason for millitary aircraft and balloons over the trenches in the first place ) has a wireless transmitter but no receiver, so they could transmit the target "square" from the map but not receive orders.
The Russian army made use of wireless early in the war - but uncoded, so the outnumbered German army, who were supposedly fighting a holding action, managed to work out what was being said and inflicted a surprise heavy defeat on Russia. https://en.wikipedia.org/wiki/First_Battle_of_the_Masurian_Lakes
This was then covered up, resulting in no one in the German armed forces thinking about this happening to their forces the other way round.
It also gave Hindenburg and Ludendorff the epithet of team military genius, though later experience showed that Erich Ludendorff's nerves weren't quite up to it - with disastrous consequences for the Michael Offensive https://en.wikipedia.org/wiki/Operation_Michael
This, coupled with the Kaiser wanting Telefunken not only to compete with Marconi marine, but also, with the deployment of hugely powerful transmitters ( eg the one at Nauen https://en.wikipedia.org/wiki/Nauen_Transmitter_Station the most powerful in the world ) to break the British under-sea cable monopoly with direct radio contact to Germany's colonies meant that German developments centred around high power transmitters at the expense of sensitive receivers, whereas in Britain a more balanced view was chosen and sensitive valve receivers were developed https://en.wikipedia.org/wiki/H._J._Round
This meant that when some ( well to do ) British hams with their new receivers started listening out towards the beginning of the war, they picked up transmissions from the K Marine base at the Jade, which the German engineers would not have expected to carry over the North Sea http://blogs.mhs.ox.ac.uk/innovatingincombat/hippisley-hut-hunstanton-wireless-interception-world-war-one/ and because of the Masurian "cover-up" no German Admirals were thinking about radio interception across the Nordsee anyway. so the Royal navy mostly got good advanced warning when the Hochseeflotte was starting an operation - including just before Jutland.
( the story about Captain Thomas Jackson, Director of Operations Division asking where the wrong German call sign was then ( wirelessly) telegraphing incorrect information to Jellicoe is apocryphal https://www.nmrn.org.uk/news-events/nmrn-blog/room-40-%E2%80%93-triumph-and-tragedy-jutland-1 https://military-history.fandom.com/wiki/Thomas_Jackson_(Royal_Navy_officer) As we know from the Titanic follow-ups, you can't just believe anything that anyone says . . . ).
...there is a 2006 account of a sailor stranded in a sinking boat at night, who flashed "SOS" with a flashilight, and was rescued by a person on land who knew CW.
Everyone should know SOS, but to paraphrase Lawrence Beesley:- Anybody know what a flashing light at sea might well mean