President Barack Obama, accompanied by Sen. Claire McCaskill D-Mo., right, greets supporters at Lambert-St. Louis International Airport in St. Louis, Mo., Wednesday, March 10, 2010, prior to speaking about health care reform and attend fundraising events for McCaskill. (AP Photo ...

FILE - General Electric's Ion Track EntryScan apparatus is shown June 27, 2006, at Lambert International Airport in St. Louis. Airport security officials have spent years exploring technology that could prevent passengers from smuggling explosives onto planes. One approach in ...