The Flossenbürg camp system had become a key supplier of Bf 109 parts by February 1944, when Messerschmitt's Regensburg plant was bombed again during "Big Week". Seven hundred Soviet prisoners who had been working at the Regensburg factory were transferred to Flossenbürg to continue working on Bf 109 production. Increased production at Flossenbürg was essential to restoring production in the aftermath of the attack. Aircraft manufacturer Arado eventually became one of the primary users of slave labor at the subcamps for the Arado Ar 234 jet bomber project, at Freiberg among other locations. Other prisoners in the subcamps were forced to work on synthetic oil production or repairing railways. Before the end of the war, about 18,000 prisoners at Flossenbürg and its subcamps were working on aviation-related projects.