Already by 1933, Sagebiel had, at his brother's suggestion, come to be at the Deutsche Verkehrsfliegerschule ("German Commercial Flyers' School"), which was a front organization involved more with Germany's air force buildup than with commercial flying. As of 1934, he was being trusted with planning, as well as overseeing construction of, numerous Luftwaffe barracks (in Döberitz, Berlin-Gatow and Kladow, to name a few) as leader of the special works unit.