Money-Saving Tricks Range From the Questionable to the Legit : Airlines are cracking down on a common technique known as ‘back-to-back ticketing,’ which many frequent travelers use to reduce fares.

One of the more common questionable techniques to reduce business air fares--”back-to-back ticketing”--is again under airline scrutiny.

“We are cracking down on it,” said Jim Faulkner, spokesman for Minneapolis-based Northwest Airlines. “In terms of how we detect it, we’re keeping that secret.” Other airlines, one by one, are tightening up their rules too, said Randy Petersen, editor of Colorado-based InsideFlyer magazine.

Back-to-back ticketing is of particular value to business travelers because it sidesteps Saturday night stay-over rules, which were created specifically to encourage leisure travelers to take trips they might not otherwise take over a weekend.

But the practice has become common enough among business travelers that several airlines are taking a hard-line stance. Northwest Airlines recently amended its tariff rules to say that the airlines may now cancel any reservation or confiscate a ticket on the spot if it even appears to be a back-to-back ticketing arrangement.

A typical back-to-back ticketing situation involves buying two round-trip discounted tickets, one originating in the city from which the traveler is departing and the other originating at the traveler’s destination. By using half of each ticket for a single trip, the traveler can sometimes save hundreds of dollars over the price of a full-fare ticket.

For example, say a traveler had wanted to fly from Los Angeles to Minneapolis for a business trip in November for two days. The full fare for such a trip would have been about $1,300. However, using back-to-back ticketing, the traveler could have made the trip by purchasing two $300 restricted air fares, each requiring a weekend stay and 21-day advance purchase. The traveler uses the first half of each of the two discounted fares, throwing the other away.

Business travelers who can plan ahead could even use both tickets for two separate midweek business trips. In the above example, a traveler could schedule a second trip to Minneapolis a few weeks later, using the return flight of the Minneapolis-originating ticket that was used to get home from the first trip.

The traveler would go home from the second trip with the return of the first flight from Los Angeles. Using both tickets is called “nesting” because one round trip (Minneapolis-LAX-Minneapolis) is “nested” inside of the other round trip (LAX-Minneapolis-LAX). In some cases, even travelers who do not know when they would travel again could be ahead by scheduling return flights for months ahead and then pay the fees for changes to set up a later flight.

But now such methods may not always work. “The word is out that Northwest is really getting tough on back-to-back ticketing,” said Terry Trippler, publisher of Airfare Report, a Minneapolis-based newsletter that keeps track of airline tariff rules and changes.

The rule changes make it possible for reservation or gate agents to decide if someone appears to be using two tickets to get around the rules, Trippler said. The agent can act if he or she even thinks a passenger is breaking the rule.

Currently, Alaska Airlines, American Airlines, America West Airlines, Trans World Airlines, and USAir have specific language in their rules prohibiting back-to-back ticketing. United Airlines, Delta Airlines and Continental Airlines do not have specific language to prevent it, but they have rules that may cover this situation, such as language that the airline will charge people full fare if they are discovered in violation of Saturday-night stay requirements.

In general, airlines require that passengers expect to complete their itinerary and reserve the right to cancel reservations or collect the full fare if passengers arrange tickets with the intent to get around fare restrictions.

Increasingly sophisticated software makes it possible for airlines to better detect people who are trying to get around the flight rules, InsideFlyer’s Petersen said. Airlines that want to discourage these practices can track passengers in various ways, including the use of frequent-flier program numbers.

Petersen cautioned that travelers risk getting caught and forfeiting both the tickets and the miles. “It’s not for everyone,” he said.

Airlines prohibit the practices not only because it costs revenue but also because it makes it more difficult to gauge load factors and sell seats efficiently.

“Back-to-back [ticketing] is breaking the rules of the contract,” Northwest’s Faulkner said. Passengers who engage in it are taking a seat away from another passenger. Then, because airlines overbook to try to compensate for people who don’t show, they sometimes miscalculate and have to pay money to passengers who are involuntarily bumped. “It’s costing us money all the way around,” he said.

For some travelers, however, the issue comes down to basic consumer rights.

They “can’t stop people from buying two fares,” Trippler said. “They don’t have a right. If they don’t like the way people buy the tickets, then just change the fares.”

Trippler and Petersen believe back-to-back ticketing and related fare-minimizing techniques are widespread.

Another popular but unethical strategy is “hidden-city” ticketing, which is invariably prohibited by the airlines. Hidden-city ticketing is used when a flight to a city beyond the stopover or hub city is cheaper than flying to the hub or stopover city itself. Travelers buy a ticket to the distant point but get off the plane at the hub. However, airlines now detect that the connecting ticket was not used and increasingly will bar a return flight when the traveler tries to return home from the hub.

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Consumers booking their own airline, hotel and rental-car reservations on the Internet computer network could produce billions in annual revenue for the travel industry, according to a survey conducted by CIC Research Inc.

CIC, a San Diego-based economic research firm, estimates that there was potential demand of $38 billion during the past 12 months for services in domestic leisure travel alone, based on the responses of Internet users. “Travel suppliers ignore the Internet at their peril,” Schonland said.