Pretending to be an airplane by spreading the arms straight out to the sides, usually while running or otherwise in motion.
In Japanese, the sound effect of an airplane flying is ブーン ("bu-n"). Consequently, airplane arms are known as "bu-n" in Japanese. "Bu-n" is also a nickname and catchphrase of "内藤ホライゾン" (Naitou Horizon), an ASCII art character who is a mascot for 2channel's VIP board.
