A short spin-off anime released on "Kouya no Kotobuki Hikoutai: Oozora no Takeoff Girls!" game app and YouTube.
AnimePiracy is a site to watch online anime like Kouya no Kotobuki Hikoutai Gaiden: Oozora no Harukaze Hikoutai SUB online GoGoAnime, or you can even watch Kouya no Kotobuki Hikoutai Gaiden: Oozora no Harukaze Hikoutai in HD quality just like KissAnime and 9Anime.