Through-Fares Offer Real Savings : Airlines: Many carriers offer complimentary flights to outlying cities in foreign destinations as part of a “through-fare” policy. But you may have to ask about it.

Free flights to other destinations once you fly to a carrier’s gateway city overseas?

That’s possible when airlines provide a “through-fare,” allowing overseas travelers to fly at no charge after their arrival to cities near their primary destination.

Also, an airline may pick up the tab for a domestic flight from a connecting city in California to its gateway at LAX if the traveler is flying out of the country on that carrier.

The same airline may allow you to reverse this procedure and fly back from Los Angeles to another city in California after your return international flight.

Through-fares, which airlines also call “common rates,” also may be available once you arrive abroad.

Depending on the size of the country you’re going to, you might be able to fly on to another city without additional charges. In a small country like the Netherlands, for example, through-fares probably would not be offered to another city from the gateway city of Amsterdam.

Many airlines offer through-fares to LAX, which can save money for passengers in outlying areas. But availability of these special fares, which can vary depending on the particular kind of basic fare involved, and time of year, is not always heavily promoted by the carriers. Check with your travel agent or airline directly for options.

Similarly, there are often many opportunities to add cities to your overseas itinerary, free of charge.

“Through-fares are part of the airline structure, and they should always be considered when you’re close to a major gateway in the United States,” said Mikki Fink of Sun Coast Travel in Westlake Village. “People are often very surprised at all of the extra cities they can go to.”

For example, SAS offers free round-trip flights to LAX from all cities in California to its passengers flying out of LAX on most of its regular and discount fares.

On Lufthansa, the fare for a Palm Springs-LAX-Frankfurt flight would be the same as if you flew from Los Angeles to Frankfurt.

Through-fares from San Diego to Los Angeles are often available. And in some cases, your international fare may be even lower. The San Diego-LAX-Frankfurt fare on Lufthansa can be as much as $43 less round trip than the LAX-Frankfurt fare.

Fares from LAX and San Francisco on the same carrier to points overseas are often identical.

Suppose you wanted to spend time in San Francisco for business or personal reasons? In some cases, an airline might pick up your round-trip LAX-San Francisco fare to catch its flight from San Francisco. Air New Zealand, for example, offers this perk on most of its fares.

Other domestic examples: Iberia and Korean Air offer through-fares from San Diego and San Francisco to LAX. Pan Am also offers through-fares from San Diego and San Francisco to LAX. Swissair provides through-fares from San Francisco, San Diego, Oakland, Fresno, San Jose and Sacramento to LAX on most of its fares, as does KLM for San Francisco, Oakland and San Jose.

On its regular and APEX fares, Air France offers through-rates from San Diego, Fresno, Monterey, San Francisco, Oakland, San Jose, Sacramento, Ontario, Long Beach, Santa Ana and Las Vegas to Los Angeles on its LAX-Paris flights.

However, if you fly Air France from LAX to Paris on its nonrefundable Eurosaver fare, only Fresno, Monterey, San Diego, Sacramento and Las Vegas have through-fares.

Moreover, these domestic flights must be taken only on USAir, whereas you can fly to LAX on virtually any carrier on the regular and APEX fares to Paris.

British Airways has launched a program of complimentary round-trip helicopter flights from John Wayne Orange County Airport to LAX. This service is available to all passengers on regular fares. If you fly first or business class, you can also opt to get a free ride to LAX through Concierge Limousine Service.

Similar benefits may be available once you arrive overseas.

Varig lets Rio de Janeiro-bound passengers departing from LAX on most regular and discount fares continue on to Sao Paulo at no extra cost.

In Europe, SAS offers through-rates from its gateway of Copenhagen with all of the cities in the mainland or Jutland part of Denmark; Oslo, Bergen, Stavanger and Christiansen in southern Norway, and Goteborg in Sweden.

However, the Swedish capital of Stockholm isn’t included in this option. You have to purchase your seat to Stockholm, but once you get there you can fly free to five other cities in Sweden: Jonkoping, Kalmar, Norrkoping, Vasteras and Vaxjoe.

“You can find many examples of through-fares in Europe,” Eileen Drutman, SAS spokeswoman, said. “They’re available most often with regular fares, but they can be utilized with promotional fares as well.”

Lufthansa lets you fly at no extra charge from its gateway city of Frankfurt to Bonn, Cologne, Dusseldorf, Hamburg and Stuttgart. In addition, Lufthansa offers its own rail services free from Frankfurt to Bonn/Cologne, Dusseldorf and Stuttgart.

If you fly LAX-Dusseldorf-Munich on Lufthansa, you can continue on free of charge to Bremen, Hanover, Nuremberg, Berlin and even Leipzig in East Germany.

Swissair permits passengers on its LAX-Zurich flights to fly to Geneva and Basel at no extra charge. And Korean Air lets you journey to Pusan, second-largest city in South Korea, from Seoul.

However, once your stay in a city is considered a stopover, rather than a connecting point, the chance to fly free to other points may be lost. Internationally, once your stay reaches six hours, it’s considered a stopover. An exception is when the next flight to your ongoing point isn’t available within 24 hours.

Some travelers take advantage of this option and book flights so that they arrive at the overseas gateway too late to catch the last plane of the day to their next point.

Generally, it would be a prudent move to have your ticket written to the farthest point you can go on a through-fare before you leave the United States. Although you can have a regular- fare ticket rewritten overseas to fly on to a common-rated city at no charge, getting it accomplished may be difficult or even impossible with a promotional fare.