Southwest Airlines will soon require travelers who don't fit within the armrests of their seat to pay for an extra one in advance, part of a string of recent changes the carrier is making .

The new rule goes into effect Jan. 27, the same day Southwest starts assigning seats.

Currently, plus-size passengers can either pay for an extra seat in advance with the option of getting that money back later or they can request a free extra seat at the airport. Under the carrier's new policy, a refund is still possible but no longer guaranteed.

In a statement Monday, Southwest said it's updating some of its policies as it prepares for assigned seating next year .

"To ensure space, we are communicating to Customers who have previously used the extra seat policy that they should purchase it

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