American does that, it seems they have about twelve categories of people that can board based on frequent flyer status, what credit card of theirs you have, military service, if your first name starts with Q, before they even get to their Zone 1 people. The one time I flew Southwest I had ticket number 55. Walking through the airport I saw a sign at their help desk about upgrading my place in line so I asked. The girl tells me she can get me spot number 5 for $15. It was a no brainier to pay it.