What is the best way to cram people into a tin can in the sky? For five decades, Dallas-based budget airline Southwest made its reputation on its unique open seating policy. Savvy passengers who checked in early got to board early, too, lining up at distinctive silver stanchions to claim first dibs on whichever seat they preferred. The fairer-than-thou approach extended all the way into Southeast’s cabins: For years, the airline had no first-class seating, and all seats basically looked the same. No longer! On Tuesday, Southwest Airlines officially inaugurated its new assigned seating policy, the last in a suite of changes that moves it closer to the mean of airline operations. Taken by itself, the new policy, which breaks passengers into boarding groups and loads them according to seat location, should be more efficient. But unfortunately for optimization enthusiasts, Southwest’s new boarding plan comes with some asterisks—concessions that executives say will goose profits—that will likely make the process pokier than it could be. First, a bit more about the new plan. In lieu of …