Das Luftschiff (1983)

Stannebein is "an inventor of air ships for the benefit of mankind," or so he sees himself and his place in world history. In order to secure financing for his fancy, he adopts to the rhetoric of the time and, unwittingly, ends up building an air base for the Nazi German Condor Legion in Spain. His protest to the German authorities is, of course, in vain. In 1945, his family starts to inquire about him, surmising that his past and his patents might be valuable. However, Stannebein's last residence, the insane asylum, stands empty.