United Continental Holdings Inc. will join Delta Air Lines Inc. and AMR Corp.’s American Airlines next year in being able to speed some of its most frequent fliers through security at some airports, U.S. Transportation Security Administrator John Pistole said.

The PreCheck participants — who must be invited and agree to provide information such as flight history to the government — often keep their shoes, belts and light coats on at designated checkpoints, Pistole said in an interview today at Bloomberg’s Washington bureau. Those fliers also can keep laptops and liquids packed in carry-ons, he said.

Better information about travelers helps the TSA “to say ’no, we don’t have to treat each person as a putative terrorist,’” Pistole said.

More than 120,000 fliers have used PreCheck since the program started Oct. 4, Pistole said. Airports in Dallas, Miami, Detroit and Atlanta have the checkpoints. Las Vegas, Minneapolis and Los Angeles airports are scheduled to have them in the next few months.

United hasn’t determined at which airports the service will be offered, Christen David, a spokeswoman for the Chicago-based carrier, said by telephone. United is the world’s biggest airline.

The company must integrate the technology systems that United and Continental, which merged last year, use for passenger services and reservations before it can implement PreCheck, she said. Those systems are scheduled to be combined in the first quarter.

“Elite tiers” of fliers from participating PreCheck airlines are invited into the program, Pistole said without specifying criteria for an invitation. U.S. Customs and Border Protection’s so-called trusted travelers also can participate.

Pistole said he wants to provide speedy screening to members of the military and travelers with government security clearances. Agency officials are exploring how to include them in a PreCheck-style program, he said.

Pistole also said he sees no technology “on the immediate horizon” that would allow passengers to keep shoes on at checkpoints. Machines to screen carry-ons for dangerous liquids, such as bomb ingredients and acids, aren’t ready either, he said.

The U.S. probably won’t be ready “from a technology standpoint,” Pistole said, to let people carry liquids larger than 3.4 ounces (100 milliliters) through checkpoints by April 29, 2013, a date set by the European Union as the expiration of the restrictions.

Pistole denied reports over the last week that two elderly women with medical devices were strip-searched at airports in New York and Fort Lauderdale, Florida.

“TSA does not strip-search people,” Pistole said. “We did not strip-search anybody in this instance.”

The agency must work to better educate travelers about what to expect in a pat-down and to allow enough time before flights, Pistole said.

Pat-downs of older fliers who refuse to pass through whole- body scanners or set off those machines’ alarms remain necessary because “terrorists are willing to exploit societal norms,” he said.

The TSA in September began a new screening procedure for children 12 and under that results in fewer pat-downs and allows them to keep their shoes on in most cases.