Hmm... true:

As originally conceived and presented in his early stories, Superman's powers were relatively limited, consisting of superhuman strength that allowed him to lift a car over his head, run at amazing speeds and leap one-eighth of a mile, as well as an incredibly dense body structure that could be pierced by nothing less than an exploding artillery shell.[98] Siegel and Shuster compared his strength and leaping abilities to an ant and a grasshopper.[99] When making the cartoons, the Fleischer Brothers found it difficult to keep animating him leaping and requested to DC to change his ability to flying; this was an especially convenient concept for short films, which would have otherwise had to waste precious running time moving earthbound Clark Kent from place to place.[100] Writers gradually increased his powers to larger extents during the Silver Age, in which Superman could fly to other worlds and galaxies and even across universes with relative ease.[98]