I guess they finally gave up on Esperanto; good idea!

Actually, various forms of English (from pidgin to US-Standard) have been serving as our planet's de facto global language for centuries, ever since Britannia began to rule the waves. By the time the British Empire's influence began to fade, the American Century was well underway, and technological/economic imperialism has taken over for political rule.

In the science-fiction novels of Orson Scott Card, a slightly-simplified version of English called "Common" is the univeral language of a human race scattered over many planets. I just read a passage in Shadow of the Giant where one character chides another for incorrect grammar: in self-defense, the accused person says "But I wasn't speaking English, I was speaking Common; the word "whom" does not exist in Common."