Taking another small step to expanding a fledgling expedited screening program, the Transportation Security Administration (TSA) this week said it is further expanding its PreCheck pilot by adding Las Vegas McCarran International Airport for operations early next year.

The agency said that US Airways will offer the risk-based screening program to eligible passengers, joining Dallas/Fort Worth, Miami, Atlanta, Detroit, Los Angeles and Minneapolis/St. Paul Airports, which are either operating with PreCheck lanes or plan to early in 2012.

US Airways joins American [AMR], Delta and United Continental in offering PreCheck to select frequent flyers who may volunteer information about themselves in applying and must be approved by TSA to participate. Participants in the program may be referred to the PreCheck lane at the security checkpoint of an airport, where the benefits may include not having to divest shoes, belts, lightweight coats, laptops and 3-1-1 compliant liquids and gels from bags.

In addition to select frequent fliers, U.S. citizens of Customs and Border Protection’s trusted traveler programs are also eligible to voluntarily apply to participate in PreCheck.

PreCheck lanes began operating in October and so far so good.

“I am encouraged by the positive passenger feedback and early results from this risk-based security initiative, and look forward to working with our airline and airport partners as we continue expanding and testing this concept,” John Pistole, the TSA Administrator, said in a statement on Wednesday.

TSA said that about 140,000 passengers have been screened through PreCheck since operations began at the Dallas, Miami, Detroit and Atlanta airports. The agency expects a “substantial expansion” of the program across the United States in 2012, Pistole said on Monday at the American Association of Airport Executive’s annual Aviation Security Summit.

The agency is also looking to expand participation in its risk-based security initiatives by adding new population sets. These include a new pilot project involving a Common Access Card (CAC) reader for military service members who have a CAC card, Pistole said. This will kick off at a regional airport in Monterrey, Calif., and if successful, may expand to a “couple of key airports” where DoD personnel travel regularly to permit expedited screening based on the information known about these people, he said.

Other add-ins for risk-based screening include those with security clearances in the intelligence and law enforcement communities, Pistole said. There also other potential populations to be added into the risk-based screening programs, he said.

TSA also looking to expand another risk-based pilot program called Known Crewmember, which is currently focused on airline pilots, to more than the existing participating seven airports, Pistole said. The goal is to get to approximately 80 to 85 of CAT-1 (Category 1 airports), the CAT-X’s obviously,” he said. “That would cover 97 to 98 percent of the pilots.”

TSA is also looking to possibly include flight attendants in Known Crewmember, Pistole said.

Pistole said it is too early to say what percentage of the passenger air traveling public may eventually be eligible to participate in PreCheck. He said he’ll have a better idea in a year.

Steve Wolfe, an aviation security technology consultant, believes that potentially between 20 and 40 percent of air travelers may use a known traveler lane at security checkpoints.

A primary reason for having trusted traveler lanes at airports is to begin narrowing the focus of screeners to people that little is known about them.