With the classic 'first-come, first-sit' era ending, it pays to have that branded credit cards or elite status when it comes to booking a flight.

(CNN) - On Tuesday, Southwest Airlines officially started selling assigned-seating fares. Travelers can now pick their seats in advance for an extra charge on flights beginning Jan. 27. Purchase options include the ability to select seats with extra legroom. Other flyers will be assigned a seat at check-in.