When TSA rolled out the precheck program (which is, basically, pre-9/11 screening where you leave everything in your bag, leave shoes on, and go through a metal

When TSA rolled out the precheck program (which is, basically, pre-9/11 screening where you leave everything in your bag, leave shoes on, and go through a metal detector in a usually-short line), they began by inviting people from the upper tiers of frequent-flyer programs into it. I don't exactly know the thinking there, but I'd guess it's that someone who flies that much is unlikely to be a risk due to having gone through their standard screening so many times. These days, though, they've gotten rid of that and now if you want precheck you have to enroll in it or get it from another trusted-traveler program (Global Entry, in my case). Some airlines have had a separate lane set up to funnel their status-holders to the front of the normal security lines, too, though that seems hit-or-miss in these days when most of the frequent flyers have precheck in some form or another.