As TSA pre-check started, United seeded it with frequent travelers, including me. At random, one still ends up sometimes without a TSA Pre-Check boarding pass. After several flights in a row without precheck, I learned that one's odds improve with an actual "Known Traveler Number" (KTN).

One gets a KTN by applying for either TSA Pre-Check or Global Entry (or NEXUS or SENTRI). Each of these programs have fees. Global Entry is a few dollars more, and as a perk also includes Global Entry, so it seems the no-brainer choice even if one only flies international once during a five year period. You'll thank yourself eventually.

Global Entry Program

The wait is substantial for the interview, for either program. Get started, now.

Once you receive a KTN, log in to United.com, "View Account", scroll to "Profile" and click on "Edit Traveler Information". Now update your Known Traveler Number. This needs to be on file with United (and anyone else you fly) to have any effect.

So yes, a form of TSA Pre-Check was free to elites, but it was inferior to the form one pays for. You get what you pay for.