Based on a five-month-old successful pilot program to expedite screening of select airline passengers, the Transportation Security Administration (TSA) yesterday said it is expanding the PreCheck program this year to 28 more airports throughout the country.

The pilot project began last October at four airports and since then has added three more. Yesterday’s announcement means that 35 of the busiest airports in the United States will have dedicated PreCheck lanes by the end of 2012. Currently, two airlines are participating with three more planned later this year.

“We are pleased to expand this important effort, in collaboration with our airline and airport partners, as we move away from a one-size-fits-all approach to a more intelligence-driven, risk-based transportation security system,” TSA Administrator John Pistole said in a statement.

PreCheck offers approved passengers’ expedited screening through a dedicated screening lane where air travelers may not have to remove several items that other passengers do including shoes, laptop computers, belts, lightweight coats, and the 3-1-1 compliant bag. The agency maintains random and unpredictable security measures so there is no guarantee of expedited screening.

Pistole’s vision is to eventually include more airports and airlines. So far, more than 336,000 passengers have been screened through PreCheck lanes, allowing TSA to focus more attention on travelers it knows less about.

Eligible PreCheck members can voluntarily apply to join the program. Participants include certain frequent flyers from participating airlines as well as members of several Department of Homeland Security trusted traveler program that are U.S. citizens and are flying on a participating airline.

TSA vets applicants for approval to join the program. Every time an approved passenger books a flight with a participating airline, information indicating that person’s eligibility is embedded in the barcode of the passenger’s boarding pass, which gets read by a TSA Officer at the security checkpoint.