How to fly cheap: the benefits of someone else's baggage. (Travelwise).

Jason Stevens of Los Angeles needed to fly to Thailand on three days notice to close a business deal but couldn't afford the $3,900 roundtrip airfare. Through a friend, Stevens heard about courier travel. After a few phone calls he boarded a flight to Bangkok for just $450 roundtrip.

Companies all over the world use couriers' checked baggage allowance to transport their cargo in exchange for drastically reduced airfare. The savings can be as much as 85% of the cost of a roundtrip ticket, according to Bruce Causey, president of the International Association of Air Travel Couriers (IAATC). At press time, IAATC was offering a roundtrip flight from San Francisco to Singapore for $150. By comparison, Internet giants Travelocity and Expedia had the same flight for $750. Causey says that although 85% is an extreme-case savings, these discounts are available often, especially if the courier/passenger is flexible and available to travel at a moment's notice.

John Ferry of the Air Courier Association says a person can book courier travel as much as 60 days in advance and in some cases all you carry is paper work, meaning you don't have to give up your baggage allowance.

The traveler's responsibilities? Arrive at the airport on time to meet a courier service representative. They will hand you the necessary shipping documents, customs forms, and ticket. At your final destination, hand the documents to a designated representative at the airport and you're done. The tickets are roundtrip with liberal return dates.

There are, however, several caveats:

* In some cases, you'll only have carry-on luggage if the company has used your checked baggage allowance.

* A companion ticket will cost full fare.

* Unless it's a rush job, expect to pay for your own hotel accommodations.

The IAATC (www.courier.org) and the Air Courier Association (www.aircourier .org) both charge membership fees ($45 and $29, respectively) to link prospective couriers to more than 30 courier companies, and both organizations can assist you in making the appropriate travel arrangements. If you would rather contact the couriers directly, look in the Yellow Pages under Air Courier Services or Messengers.