May 6--Federal regulators have approved the June start-up of Orbitz, a controversial new Internet site controlled by the five largest U.S. airlines, for selling air tickets and other travel services. 

Officials of the www.orbitz.com site hailed the decision by the U.S. Department of Transportation as a "green light" for what they say will be a wonderful new service travelers can use for finding low fares. 

But just as a yellow caution flag is raised when there's potential trouble ahead on an auto racetrack, the federal overseers added that they would keep a close watch on Orbitz for any violations of antitrust laws that prohibit collusion to restrain competition. 

The Orbitz site has a spiffy look and uses an advanced search engine that makes it fast and easy to use. Tickets on dozens of other airlines besides the five in control, including some carriers that specialize in low fares, will be available for purchase through the service. The Orbitz owners have promised that they won't use the site in a way that keeps other airlines from featuring their lowest fares. 

So what's the big deal about Orbitz? After all, aren't we moving steadily toward buying more and more stuff online, especially travel? Why have other online travel services, consumer groups, travel agents and some of the most successful low-fare airlines worked relentlessly in recent months trying to stop Orbitz? 

Simply put, lots of folks don't trust the Orbitz owners -- American, Continental, Delta, Northwest and United Airlines. The carriers have what many of their customers, regulators and industry experts consider a dismal record when it comes to encouraging vigorous competition that benefits consumers. And it's a record that could get worse, the critics say, if contemplated mergers of the major carriers go through. 

At their fortress hubs in cities nationwide, the big carriers have a choke hold on most business travelers' wallets. Customer service complaints are at an all-time high, and on-time performance is lousy, albeit for a variety of reasons that aren't all the airlines' fault. Repeated studies have shown that the only air routes with consistently low-to-moderate unrestricted fares are those served by somebody besides the big boys, including AirTran, American Trans Air, Frontier, JetBlue and Southwest. 

The battle over Orbitz has been fought in recent months by dueling consultants working for the two sides. 

First came a long and complex study done for Orbitz by Global Aviation Associates of Washington and Aaron Gellman, a transportation professor at Northwestern University. The study focused on how much the airlines pay for using the traditional methods of ticket sales, which used to be called computerized reservations systems and now are known as global distribution systems, or GDS's. 

These are the networks, ironically started by the major airlines themselves but now mostly independently owned, that have been used by travel agents for three decades and that now power other Web sites that will compete with Orbitz. Travelocity and Expedia are the two largest of these competitors. 

The Orbitz-sponsored study concluded that the global distribution systems have raised the fees they charge the airlines an average of 7 percent a year for the last decade, a period of rapidly decreasing computing and telecommunications costs. These booking fees are passed on to consumers by the airlines in the form of higher fares, and the smaller the airline, the greater the burden on their low-fare structure, the study said. 

"Airlines and their customers are paying a heavy price to meet the demands of these archaic computer systems," said Global Aviation managing director Jon Ash. "The GDS's, which 20 years ago provided value to the industry, now are impeding progress." 

To argue against Orbitz's start-up, the Interactive Travel Services Association, which represents other online travel services, joined forces with the American Society of Travel Agents and Southwest Airlines, and hired MIT economics professor Jerry Hausman. He determined that Orbitz would become the "market power ringmaster" of online travel sales, controlling the business to such an extent that consumers eventually would pay $3.2 billion in higher fares. 

The Orbitz Web site will be operated in a way that will make the discount fares of new-entrant airlines less visible to consumers, Hausman contended. And Orbitz will let its major-airline owners instantly share information about "secret price cutting" that isn't available to travel agents or other travel Web sites, he said. 

Hausman characterized as "absurd" Orbitz's assertion that it was needed to counteract the market power of Expedia and Travelocity. Those two sites have a 54 percent market share for independent travel Web sites, but sell only 25 percent of all Internet tickets, including those of the airlines themselves, and only 1.25 percent of all airline ticket sales, the study found. 

Since they were released two months ago, Hausman's conclusions have been endorsed by more than a dozen consumer groups. 

If these competing studies confuse you, don't worry. You're not alone. But in the meantime, consider a fact that both studies cite: About 75 percent of all airline tickets continue to be sold not by the airlines or over the Internet but by traditional "brick-and-mortar" travel agents. 

That percentage is expected to decline slowly as online sales steadily rise. But airline customers apparently are willing to pay the service fees that agencies now must charge clients as their commissions from airlines have declined. 

And why are they willing? Some of it is for having someone else deal with the hassle of booking air travel. But a large part of it may just be one of the fundamentals of any business transaction: It's a matter of trust. 

Send your question or comment about business travel to Tom Belden at The Inquirer, P.O. Box 8263, or e-mail at [email protected]. 

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