U.S. carrier AirTran Airways said beginning in March 2012 large passengers might be required to purchase an extra seat if they fly in coach. AirTran is adopting the policy in place for 30 years at Southwest Airlines. The AirTran policy would be enforced at the \"carrier\'s sole discretion,\" the Atlanta Journal-Constitution reported Thursday. Southwest said the policy is enforced with \"far less\" than 0.5 percent of its customers, the newspaper reported. Still, the policy has the effect of leaving some passengers \"embarrassed and humiliated,\" said Peggy Howell, a spokeswoman for the National Association to Advance Fat Acceptance. \"I\'m sorry to hear that they\'re now going to be passing on their bad policy to another airline. We are paying customers,\" Howell said. Howell also said, \"They leave it up to the judgment of their staff,\" which means there is no specific chart customers can use to anticipate paying for two seats. \"The armrest is considered to be the definitive boundary between seats,\" Southwest says on its Web site. At some point, the airline said, it could no longer ignore \"complaints from customers who traveled without full access to their seat due to encroachment by a large seatmate whose body extended into the neighboring seat.\" The policy for both airlines includes the caveat that if the flight does not oversell the airlines will refund the cost of the extra seat to the passenger.