The motive for the hijacking remains unclear, though some reports say the pilot was demanding to speak to the brother of a female astronaut ( Judith Resnik), who perished in the US Challenger space disaster in the 1980s.
German television reports said the man had told authorities he wished to commemorate the astronauts' deaths.
He is the webmaster of a side, dedicated to Judith Resnik:
Astronaut Judith Arlene Resnik (1949-1986) - Links