Jor-El, in the hours before Krypton's destruction, argued that the Phantom Zone might be used to save the Kryptonian people — that they could be suspended within the Zone until a single individual might travel by starship to a habitable world, and then release the survivors. The Science Council roundly rejected the proposal, objecting to the idea of imprisoning innocent people alongside criminals.
Nonetheless, a Phantom Zone projector was sent to Earth with Kal-El when Jor-El used his prototype starship to save his son from Krypton's doom. Years later, Superman would inadvertently release the criminals Jax-Ur and Mala from the Zone. The two would wreak havoc on Earth, even imprisoning Superman himself in the Zone: Superman was soon freed with the assistance of Professor Emil Hamilton, and the two criminals were ultimately returned to their extradimensional prison.
Some time later, Superman and the other founders of the Justice League would imprison the destructive creature called Doomsday in the Phantom Zone, as no other method short of execution could reliably restrain the monstrosity.