I read in another thread that TSA may assign Precheck randomly to passengers who haven't enrolled in the Precheck program. However, I had a recent experience while traveling with family members where I still can't believe it's "random," and I'm curious if there's another explanation.

The 3 of them travel infrequently (1-2 flights per year), but all 3 had Precheck on their boarding passes on both an AS flight and a WN flight. They've never enrolled in Precheck or Global Entry and have no idea how they got it. They also said it wasn't the first time it had happened!