Slash air costs by traveling as a courier. `Working vacation' takes on a special meaning for air passengers who save money by escorting business cargo.

IT was 10 p.m., and I was standing in the luggage-claim area of the Los Angeles International Airport, next to a mountain of large cartons. I was the passenger-courier who had brought them from New York for delivery the following day. A casually dressed stranger approached me, identified himself as the Los Angeles representative of the courier company for which I was traveling, took possession of my ticket and luggage claims, and wished me a pleasant evening.

I had just taken my first of many trips as a free-lance courier.

In exchange for providing this service, I was charged less than half the normal ticket price. I never touched the cargo. I was driven to the airport in New York and handed a ticket and a whole lot of luggage claims.

Trips like mine have become possible because businesses have learned that the fastest way to get a package to New York, Los Angeles, London, Tokyo, or Sydney is by sending it as luggage with a passenger. Unlike airfreight, it is unloaded immediately.

Businesses with an urgent need to send something to a distant city pay air-courier firms handsomely for guaranteed overnight delivery. Courier shipments usually go between major cities. In the United States, New York, Washington, Los Angeles, San Francisco, Miami, and Chicago are some of the cities with courier companies.

Flights go not only between some of these cities but to Europe, the Far East, Mexico, Bermuda, and South America. The traveler will usually be required to act as courier on a round trip of one or two weeks' duration, but there are variations.

Sometimes no courier is required for the return trip. Sometimes returns up to several months later can be arranged. Occasionally the courier is handed a ticket with an open return.

Since most shipments are to business addresses, there are few flights on weekends, except on the international routes. Couriers must use carry-on luggage only, since the company uses the full luggage allowance for the cargo. Occasionally the company may put your bag into one of its packages, or you may be allowed to check it through for an extra charge, but this needs to be arranged ahead of time.

If a visa is required, the courier company will give you a letter to the appropriate consulate, which will usually issue a visa within 24 hours. If you don't live near a consulate, find out if there is one in the city where the flight originates. If so, phone ahead and tell them you'll be bringing in a letter and will need an instant visa. Plan to be in the city during office hours. Most consulates are very accommodating.

Prices vary according to company and season. Charging the passenger-courier half the full price is common, but lower prices are possible. Recently, trips from New York to Buenos Aires and Rio de Janeiro have been available for $350 round trip and to Los Angeles for $100. Round-trip courier tickets from Los Angeles to Hong Kong have been priced at $340, to Singapore at $325. Payment is customarily by check or money order, though some companies do accept credit cards.

When the round-trip courier fare is cheaper than the regular one-way fare, a traveler might be tempted to buy it for a one-way trip, the companies have discovered; to make sure the courier is available for the return, a deposit is usually required, which is refunded when the courier returns.

Since no shipment can be sent without a courier, there are times when the company needs you more than you need it - and a super bargain price or even a free trip can be negotiated at the last moment. Examples of trips that have been available recently for next-day departure: a $99 round trip to Europe and one for $50 to Australia.

Couriers can reserve a travel day up to two months in advance with most companies, but the company selects the flight. As a rule, one courier per flight is sent. If you have a traveling companion, he or she may be able to travel to the same place as a courier a day before or after your flight, or as a full-fare passenger on the same flight. Sometimes two people can fly on the same day with two different courier companies - and even end up on the same plane.

On domestic flights the courier's name isn't on the ticket, but on international flights it is. This means that, in addition to flying cheaply, the courier may be able to take frequent-flier credit on overseas trips.

No shady cargoes

In transit, the courier is a passenger like any other. His or her main job is simply to take the shipping documents from one airport to another, and on international flights he has the additional task of putting the cargo through customs.

According to Kenneth Clarke, editor of Travel Secrets, a monthly newsletter about courier travel, couriers don't need to worry about being used to transport anything shady across frontiers, and ending up in big trouble far from home. The courier companies are respectable businesses that want to guard their good reputations, he says. What's in the packages? Documents of all sorts, bank records, critical spare parts, videotapes, photographs, and blueprints.

How to find a company

There are several ways to get in touch with a courier company. Check the Yellow Pages in major cities under ``air courier services.'' Only a few use free-lance couriers, and destinations and prices must be explored. With perseverance, one can find a courier flight through the phone book.

For a small fee, there are easier ways. Mr. Clarke has built a business here in New York around his vast knowledge of courier flying. In addition to adult-education seminars on the subject, Clarke has put his material on a tape and sells it by mail (see box at right), together with a fact sheet that lists many courier companies, their current destinations, and prices. Travel Secrets also gives his list of companies, updated monthly.

Such a list can be helpful, since things change constantly in the courier industry. A recent Travel Secrets issue issue lists 20 companies in New York, Los Angeles, San Francisco, Chicago, and Miami and dozens of destinations and prices as low as $100 round trip from New York to London or Los Angeles. Travel Secrets also reports on inexpensive accommodations, car rentals, cheap flights for non-couriers, and other tidbits.

Instead of dealing directly with courier companies, you can use the services of an agency. For a fee, they'll match people who want to be couriers with companies that need them. The biggest, Now Voyager in New York, was founded by Julie Weinberg, herself a frequent courier. Now Voyager sends out over 100 couriers a week.

At this writing, the agency is booking flights to Athens, Amsterdam, Bermuda, Buenos Aires, Brussels, Hong Kong, London, Madrid, Mexico City, and other destinations. Now Voyager charges a $45 administration fee, good for a year, paid the first time one buys a ticket. When one wants another ticket, the destination may no longer be available; so go only if you save at least $45 the first time out. Usually you will.

When no courier has signed up for a coming flight coming up, the last-minute savings can be great at Now Voyager. These bargains are announced on an after-hours tape on the agency's answering machine. Tickets can be ordered by phone and charged to a credit card.

The duties

Couriers, no matter for whom they fly, are subject to certain rules and may be asked to sign a document on which the rules are spelled out in detailed and possibly intimidating language. Read it carefully, but don't be dismayed. What companies really expect is reasonable: You must check in when expected; you absolutely must not lose the manifest pouch; and you must hand it over to the company representative at the airport, after landing. You must be dressed and groomed appropriately, and you must abstain from alcohol on the flight.

If these rules fit in with your expectations, you may find courier travel pleasant and rewarding.

How to get more information on travel as an air courier

Here are details on two organizations that can be especially helpful to novice or experienced passenger/couriers:

Kenneth Clarke, P.O. Box 2325, New York, NY 10108. Mr. Clarke's $15, by-mail tape explains air courier travel in great detail. It is sold with a fact sheet that lists courier companies. Some of the facts, especially destinations and prices, may change between the time the tape was made and the time you buy it. Clarke's newsletter Travel Secrets gives the same basic information, but destinations and prices are updated monthly. A one-year subscription costs $30. You can also write for information about seminars.

Now Voyager, 74 Varick St., New York, NY 10013 (tel: [212] 431-1616) offers information and bookings for courier trips. Annual administration fee: $45. The office is open Monday through Friday from noon to 5 p.m.; at other times an answering machine lists available flights and last-minute super bargains. The number can be hard to reach, though; even in the middle of the night one often gets a busy signal.