If you've recently heard ads touting ways to get through airport security more quickly, you might wonder how it works. The Transportation Security Administration has set up a Registered Traveler program, under which private firms run a thorough background check and use biometrics such as fingerprints and iris scans. There are six approved programs, with one being Verified Identity Pass, offering the Clear card for $100 a year. But the fast lanes are only at 13 airports, sometimes only at certain checkpoints and for certain airlines. The overall Registered Traveler program has drawn criticism for privacy and security reasons. The American Civil Liberties Union says it is "based on intrusive but ultimately ineffective probes into travelers' lives." Some say it could aid terrorists, who could get recruits with clean records so that they can speed through security checkpoints more easily.