But of course, your daily commute releases more CO2 than the occasional long-haul flight. So unless you ride your bike to work everyday, this is a premature optimization.

Well, I do bike to work. But that's beside the point.

All calculations I've seen conclude that driving alone actually is less carbon-intensive than flying, on a per mile basis. The average American drives 10-15k miles per year. If you fly even remotely often, you'll easily end up logging more air miles than car miles. And if you carpool, there's no contest.

Flying is way worse than you may think, from a CO2 point of view.