There's a plane symbol on this international world rate Belgian stamp. Interesting that the word world is in English, and that the design is a stamp and airmail sticker combined. And I'm not sure what to say about the color choice (sickly green?) not to mention King Philippe's expression on this stamp.
And an angel from Royal Mail's Christmas 2007 stamp set.
To see more things that fly on postage, explore the links at Sunday Stamps.