Israel uses private security companies at their airports ...
and everyone agrees they have the toughest airline security anywhere. The Department of Energy uses contractor security personnel to guard nuclear weapons facilities.
A private company or its employees can be fired for failure. Try doing that to a federal employee other than the military. Look at how responsive, efficient and reliable federal employees are at places like the IRS, INS, and the post office. Sorry, but this idea of federalizing airport security personnel just doesn't make any sense.