I was curious to know if another email app used paper airplanes to represent drafts before Apple Mail did. I went out Googling and found all manner of representations, usually employing the paper envelope, or another snail-mail related symbol. None of them, except Mail, uses a paper airplane. So my modest research suggests that the use of a paper airplane was a pretty novel bit of design. Was it an Apple innovation, or did it debut in some prior app I haven’t been able to track down?After all these years using Apple Mail, I never before noticed that the Drafts icon is a sheet of paper with a folding diagram to turn it into an airplane.
Daniel Jalkut, on the use of paper airplane icons to represent sent email: