Now that Southwest Airlines has become the busiest carrier at Florida's Orlando International Airport, the carrier is considering international routes that could start with Caribbean destinations. CEO Gary Kelly says expansion fits nicely into Southwest's plans after a banner year in 2009, when "our people responded with some of the best operating performances that we've had in years. No. 1 in customer service. And our 37th consecutive profit..." Southwest will add its 69th city on May 23, when Panama City, Fla., becomes a destination.