<p>The heightened security surrounding air travel during this Thanksgiving holiday comes months into a federal effort to plug holes in the nation's aviation safety net — from revelations about lax screening at TSA checkpoints to criminal charges against airport employees accused of smuggling guns and drugs.</p><p>One <a href="https://www.politicopro.com/transportation/whiteboard/2015/07/dhs-johnson-outlines-plan-to-fix-the-tsa-056713" target="_blank">crackdown</a>, which the Department of Homeland Security imposed months before the latest terrorist attacks in Egypt and Paris, includes measures that travelers will notice at U.S.