Strike Witches: Aozora no Dengekisen - Shin Taichou Funtou Suru!

The Strike Witches take under their wing a candidate commanding officer from the Fuso Empire, Junko Takei. She contacts the 501st to inform them that she will be meeting up with them during a training exercise. At the same time, the military announces a new operation: to make a concerted strike against the Neuroi at the Gallian coastline and establish a new frontline base.

[From Wikipedia]