Strike Witches + K-On = Sora no Woto
The first time I discovered Sora no Woto I called it a cross between K-On & Strike Witches. Well now that the series has finally debuted in Japan & on Crunchyroll, it looks like I'm not the only one who thinks that! Both 2ch & 4chan have gone wild with this image.
Source: http://www.sankakucomplex.com/2010/01/14/strike-witches-k-on-sora-no-woto