PreCheck is the TSA program that lets you bypass the lengthy “standard” security lines at US airports. If you have PreCheck you can use the short line, leave shoes on and leave liquids and computers in your carry-on luggage.
Now Frontier and Spirit have indicated that they will join PreCheck…the last US-based carriers to do so.
The hangup has evidently been mostly the changes to their reservation systems needed to get that little PreCheck logo printed on boarding passes.
Passengers can get PreCheck in several ways. My favorite is to get Global Entry ($100 / 5 years), which includes PreCheck as a free bonus.
Another way is to sign up for PreCheck itself ($85 / 5 years). A third way is through some premium credit cards.
In the past the TSA granted temporary PreCheck to randomly-selected passengers, but the agency has stopped doing so.