Josh Barro discusses the most divisive, class-oriented issue in the country today — the order in which we get to board airplanes. I never really understand it on any airline other than Southwest and I'm not always certain I understand it on Southwest. I just know I need an overhead space for my carry-on and I will certainly get it if I'm in Boarding Group A, probably get it if I'm in Boarding Group B…and there's a chance (but not a good one) I'll get it if I'm in Boarding Group C.