U.S. Transportation Security Administrator John Pistol told Bloomberg News that United Continental Holdings' top frequent flyers will join Delta and American airlines' top flyers in being able to speed through security at some airports sometime in 2012. Those who opt in to the TSA's PreCheck program must be invited and agree to background checks. In exchange, they often keep their shoes, belts and light coats on at security checkpoints and also can keep laptops and liquids packed in carry-ons.