DALLAS (AP) — A newly released air traffic control recording captures the confusion when a Southwest plane landed at the wrong Missouri airport in January.Southwest Airlines Co. said Monday that the captain and co-pilot remain on paid leave pending the outcome of the National Transportation Safety Board's investigation of the Jan. 12 incident. Both men have at least 12 years of experience at the airline.In a recording released by the Federal Aviation Administration, an air traffic controller at the main Branson, Mo., airport can be heard clearing Southwest Flight 4013 to land.After the plane stopped, one of the pilots radioed, "I assume I'm not at your airport.""Southwest 4013," the controller answered, "uhm, have you landed?""Yes."The Branson tower called a regional air traffic center in Springfield, Mo., to check on the plane. Then he relayed news that the pilot said he had landed at the wrong airport. The plane had touched down at another and smaller Branson-area airport."Are you kidding?" an official in Springfield responded."No, I'm not," the Branson tower answered.The Southwest pilots landed at night by sight instead of using instruments to guide their approach. They had to brake hard to stop the Boeing 737 with 124 passengers before the end of the smaller airport's runway. The runway there is only about half as long as the one at the main Branson airport. There were no injuries.Aviation experts have questioned why neither pilot realized the mistake before landing.