Aircraft were the arch nemesis of submarines, against which there was little defense except to evade by diving.  Attempting to develop a more effective counter defense, in August 1942 the Kriegsmarine converted four Type VIIC U-boats into "flak U-boats" which replaced the main deck gun with additional anti-aircraft platforms.  The design was initially highly effective in the Mediterranean, but became counter productive after the Allies adapted to using high yield surface bombs to completely destroy the flak U-boats with a single hit.  Aircraft which appear in Silent Hunter III  are as follows.