TSA has just introduced a new program called Gateside by TSA PreCheck at 13 airports. Eligible TSA PreCheck members can apply to go through security and enter the gate area without a plane ticket, which could be useful for parents accompanying children, grandparents helping with family travel, or meeting family members during a layover. You just have to apply 1-3 days in advance, and approval is required. The program is currently limited to participating airports but is expected to expand.  Check out https://www.tsa.gov/precheck/gateside-tsa-precheck for more details and airports.