What good is privilege if you don’t know you have it or don’t know how to use it?

Passengers eligible for TSA’s PreCheck program offering expedited security screening at 40 airports are sometimes unaware of their status and unsure of which checkpoint line to join.

So Delta, United and US Airways are now alerting qualified passengers to their PreCheck status with a “TSA PreCheck” alert on mobile and paper boarding passes.

“All TSA PreCheck participants are vetted for eligibility each time they fly,” said TSA spokesman David Castelveter. And knowing their status prior to arriving at airport “helps passengers effectively route themselves to available TSA PreCheck lanes,” he said.

While much appreciated by eligible travelers who can leave shoes and light jackets on and 3-1-1 compliant liquids in their bags, the system still has a few wrinkles.

Only some airlines in the PreCheck program currently add the alerts to boarding passes and not all boarding pass systems support the PreCheck notification feature.

Delta and US Airways passengers will see “TSA PreCheck” on printed boarding passes and, by the end of this week, the TSA PreCheck logo will be on those airlines’ mobile boarding passes. On United, the TSA PreCheck logo is currently only on printed boarding passes.

Another issue: because neither TSA nor the airlines filter by airport, “the TSA PreCheck pre-notification indicator will continue to appear on those selected customers’ boarding passes whether the airport has a TSA PreCheck screening lane or not,” Delta Air Lines spokesperson Michael Thomas told NBC News.

To solve that problem, TSA encourages passengers to bookmark and check the list of participating airports and checkpoint locations on the PreCheck chart and the TSA mobile application.

More details on the PreCheck program and eligibility are on the TSA website.

(My story about the TSA PreCheck program first appeared in NBC News.com)

Thanks for visiting Stuck at the Airport. Subscribe to get daily travel tidbits. And follow me on Twitter at @hbaskas and Instagram.