The decision of when to get in line to board an airplane can be a contentious one, but it shouldn't be. While gate agents will give clear, boarding group-specific directions , there remains a strong contingent of passengers who either get in line before they're called or wait in their seats until they're the last to board. While the latter type of traveler often hangs back to avoid standing in line altogether, the motives driving the former group can be harder to place.Subscribe to The Post Most