Southwest Airlines is considering expanding its fleet next year despite severe industry turmoil, a move that could usher in more growth in Denver.The nation's only profitable carrier might add 14 new planes in 2009 and keep flying up to 10 aging aircraft it had planned to retire this year, Southwest Chief Executive Officer Gary Kelly told Bloomberg this week.Southwest, which is benefitting from contracts it previously cemented that lock in the price of fuel, said it will see how the cutbacks at other carriers play out before making any growth decisions.The airline has taken advantage of its struggling competitors in Denver, announcing plans this year to increase service by about 75 percent. Southwest considers Denver a primary focus city and has indicated it would like to continue growing here going forward.