(CNN) – Southwest Airlines is changing its seating policy for plus-size passengers.

Starting Jan. 27, passengers who take up space in the neighboring seat will have to buy an extra ticket, and it might not be refunded.

The current rules allow flyers to buy an extra seat ahead of time and get refunded later, or request an extra seat at no charge at the airport.

Those options made Southwest popular with many plus-sized passengers.

But the new rules mean the second seat will be nonrefundable unless the flight departs with at least one open seat and both seats are purchased within the same fare class.

The move is the latest in a series of changes for Southwest.

The carrier has also ended its open seating policy and instituted checked baggage fees.

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