Southwest Airlines passengers are making their final boarding-time scrambles for seats as the carrier prepares to end its signature open-seating system. Customers on Southwest flights will have assigned seats starting on Tuesday. The airline began selling tickets shaped by the new policy in July. New airfare tiers include the option of paying more to get a preferred seat closer to the front of a plane or seats with extra legroom. An eight‑group boarding structure is replacing the find-your-own-seat scrum. Southwest says the boarding groups are based on seat location, fare class, loyalty tier status and benefits from the airline’s credit card rewards program.