Buying airline tickets on the Internet for the first time, Mary Green searched conventional sites like Travelocity but found another site with cheaper fares.

“They were less expensive,” the 42-year-old Lawrence woman who works in human resources said of Cheapflights. “May as well get the least expensive if it’s taking me to the same place.”

Sites like Orbitz, Expedia and Travelocity are popular with many people looking to save money on things like airfares, hotel rooms and rental cars. But some shoppers have discovered a new breed of special search engines that promise to dig up even better bargains.

Search engines like Cheapflights, Mobissimo, SideStep, Qixo, Kayak and Farechase look through Web sites of travel suppliers. After a selection is made, the travel engines send people directly to the supplier’s Web site to complete the purchase.

They collect referral fees from the travel suppliers, but those commissions generally fall about 50 percent below the costs triggered by a booking at one of the three major online travel agencies — a difference that leads to lower prices.

San Francisco-based Qixo is the only travel engine that charges consumers to use its service.

Millions of travelers turn to their computers whenever they plot their itineraries. Forrester Research estimates 29.4 million U.S. households will use the Internet to book travel in this calendar year, spending $53 billion in the process.

Green ended up buying her tickets in September from Expedia because Cheapflights didn’t have enough tickets for the right dates. She said she would check Cheapflights again.

Steven Sullivan, of Lawrence, typically gets his tickets by flying standby. But the 22-year-old glassblower said he planned to ask his Internet-loving dad to search the new travel engines for him.

“You go to the airport, get a standby ticket; you pay about half-price for a ticket,” said Sullivan, who plans to visit Las Vegas soon. “But it’s kind of a pain sometimes because you end up waiting around the airport longer than you want to. Many hours, you know.”

The search engines also say they pull fares from suppliers that aren’t represented by the major travel agencies.

Several travel engines include fares from JetBlue in their indexes. SideStep, the oldest travel engine, includes the entire inventory of Southwest Airlines, the industry’s longtime discount leader.

Neither Southwest nor JetBlue list their fares through the online travel agencies — a void that has prompted many consumers to consistently visit three or four travel Web sites to ensure they are getting the best deal.

The travel search engines depict themselves as a one-stop shop.

Searching the sites can provide mixed results. Mobissimo and Qixo recently found fares between $35 and $185 cheaper than Travelocity, Expedia and Orbitz for a flight from Kansas City to Mexico City.

But all five sites listed similar prices — ranging from $228 to $234 — in a search for a flight from Kansas City to Chicago.

With the advent of sites like Travelocity, Orbitz and Expedia — and the new travel search engines — some may wonder if traditional travel agencies may go out of business.

Anne Walters, general manager of Carlson Wagonlit Travel/Sunflower Travel Service, 800 Mass., said her business sold fewer airline tickets than it used to.

That’s why her business is focusing more on booking tours for customers to places such as Boston or China, or on cruises. The travel agency also is focusing on group trips.

Booking tours and cruises is more difficult on the Internet than buying airline tickets, she said.

“You’re not just going from Kansas City to Chicago and returning,” Walters said. “It’s more complicated. It’s a special vacation.”

John Novotny, vice president for operations at Travellers Inc., 831 Mass., said people often called his travel agency and quoted a price they found on the Internet.

“We’ve got the same thing,” he said.

Not everyone is convinced the newer travel search engines are bound for success.

Though such engines do offer a few convenient features, the sites still haven’t proven that they will be compelling enough to overcome the higher name recognition and deeper pockets of Expedia, Travelocity and Orbitz, said Henry Harteveldt, a Forrester Research analyst .

As of mid-November, the top six travel search engines had a combined 0.42 percent share of all traffic to online travel sites, according to Hitwise, an Internet research firm. In contrast, Expedia, Travelocity and Orbitz had a combined 16 percent share of online travel traffic, Hitwise said.

Meanwhile, the online travel agencies seem intent on preventing the search engines from gaining more ground.

Travelocity, Orbitz and Expedia are becoming increasingly choosy about which search engines they allow to crawl through the fares on their sites — and even have banned some engines from using the data.

Rob Fitzgerald, 42, said he hadn’t bought an airline ticket from a travel agent for about five years. He thinks it’s easier to buy online.

The Liberty Hall cinema manager, who buys airline tickets three to six times a year from Travelocity, said he would check out the new travel search engines.

“Expedia and Orbitz both seem like they’re more expensive,” he said. “I might be dead wrong, but that’s my impression. To be a good consumer, you’ve got to look at the best price.”

This story includes information from The Associated Press.