Superman possesses flight capabilities; Flash possesses speed. Both are superpowered beings in DC Comics canon. Racing to the edge of space would involve acceleration and sustained velocity in a vacuum environment. The claim introduces a third participant and names this person as the certain victor. Neither Superman nor Flash is mentioned as achieving second or third place; only that a different category of being achieves first. This isn't a competition among superpowers. It's domination of an entirely different tier.