The key to a "flying donkey" is an audience, much like the Bullwinkle.
The Flying Donkey is performed like this:
The male kneels on the surface of intercourse so he's sitting on his heels. In this position he is fully inserted in to the female who is on her back with her buttocks on the male's thighs. At the moment of climax, the male makes flapping motions with his arms and produces a sound like a donkey trying to overcome gravity.
... and then I got her in my lap, threw my arms out, and did my bestflyingdonkey!!
Boys who enjoy yaoi (a genre in Japan that contains sexual and/or romantic relations between two men); literally translates to "rotten boy"; corresponding female : fujoshi