TIL: The French Aéronautique Militaire was the first airforce to adopt the cockade, or Roundel, emblem for their planes in 1909. Several of their allies around the time if WWI followed suit. The existence of the cockade goes back much farther however, all the way back to medieval knights using cockades on their helmets in order to make sure their allies could distinguish them on the battlefield, as many knights heavily decorated/customized their armor individually(please correct me if I'm wrong, I'm very very far from well read on the subject).

I can't, however, seem to find out why the roundel in and of itself became so ubiquitous in the early 20th century, a quick scroll through a collection of Airforce emblems over the years shows several nations all adopting the Roundel in a relatively short time between 1909 to 1950 or so. Is there any specific reason the Roundel in particular was so popular, or was it just an aesthetic choice that people thought simply looked good?