TSA PreCheck is a service provided by Southwest Airlines that expedites airport security screening for qualified passengers. Southwest TSA PreCheck You can expedite the TSA PreCheck process by leaving liquids and laptops in your bag and wearing light jackets, belts, and shoes. You must register for TSA PreCheck and get a Known Traveler Number (KTN) on the TSA website or an enrollment center in order to be eligible. If you add this number to your Southwest profile, your boarding pass will reflect TSA PreCheck, making your trip more organized and productive.