The Transportation Security Administration's PreCheck program expanded at two airports this week. On Tuesday, the program kicked off for US Airways flyers at Washington, D.C.'s Reagan International, and the following day it became an option for United passengers at Chicago's O'Hare International Airport. The pre-screening program is open to select frequent travelers who opt to provide their personal information to the TSA. Those travelers selected will be deemed lower security risks, and might be led to an expedited security screening line that allows them to keep wearing their shoes, light outerwear and belts, as well as to pass through without removing laptops or compliant liquids and gels from their carry-on bags. Both United and US Airways are inviting eligible members of their frequent-flyer programs; United MileagePlus members also can apply at united.com/tsaprescreening. The TSA will determine eligibility for participating passengers before each flight they take, and embed the approval in the barcode of the customers' boarding passes. More information, including all participating airlines and airports, is available at tsa.gov.