Simoun(2006)

Simoun is an anime series set in Daikuuriku, a world where everyone is born female and chooses their sex at age 17. The peaceful theocracy of Simulacrum relies on magical flying machines called Simoun, which only pre-adolescent girls can pilot. When the industrialized nation of Argentum invades to steal Simoun technology, the young Sibyllae pilots are thrust into an unequal war. The series blends aerial combat with coming-of-age themes as these girls navigate identity, duty, and survival during wartime.