Most big U.S. airlines tell you even their "nonrefundable" tickets are "reusable," meaning that if you cancel your flight, you won't get your money back but you can use the value of your ticket toward a future ticket, less an exchange fee. Of course, you have to cancel before the departure date. But that promise has become a bit iffy lately. Some of those airlines charge what amount to punitive exchange fees - high enough to call into question the airlines' basic honesty in advertising reusable fares.Currently, if you cancel a nonrefundable ticket, only Southwest allows you to apply the full value of the ticket toward a future trip, with no fee at all. According to the most recent information I have, for domestic travel, you pay $75 on AirTran, Alaska or Virgin America; $80 on Spirit; $100 on JetBlue, Delta, Northwest, Frontier or Midwest; and $150 on American, Continental, Hawaiian ($30 for inter-island), United or US Airways. Don't be surprised to see further hikes in those fees as the airlines keep squeezing more and more extras out of their customers.International exchanges are even more complicated. Depending on airline and destination, exchange fees can be as high as $250. Moreover, some airliners allow exchanges, even with a fee, on only the return portion of a round-trip ticket. And many low-price international tickets are totally nonrefundable. Also, some tickets have always been totally nonrefundable and nonreusable, among them many consolidator discount tickets and tickets you buy through Hotwire or Priceline.Ticket exchange has a spotty history. When nonrefundable tickets were first introduced, they were totally nonrefundable under ordinary circumstances but refundable in the case of an emergency. However, the airlines rapidly found that savvy travelers could easily obtain or forge doctors' notes or other emergency documentation, and ruling on individual cases got to be a major headache. Partly in response to this problem, the airlines decided to keep the cheap tickets nonrefundable (no money back) but make them reusable, with a fee. Initially, most charged only $25 and, at that level, the system was fair and practical. But as the airlines became increasingly greedy, most hiked fees to their current onerous levels.As a partial offset to the fee increases, some still allow no-fee cancellation in the very limited case of death of the traveler, a travel companion, or a close family member, with a death certificate required. For now, Southwest is the obvious consumer-friendly champ. Not only does it still allow you to retain the full value of your ticket if you have to cancel, but - for travelers age 65 and up - it also sells fully refundable senior fares that are usually higher than the cheapest options but less than refundable tickets for travelers of any age.Clearly, you're at some financial risk any time you buy any nonrefundable ticket (except on Southwest). If you have to cancel a trip, at best, you're on the hook for a fee that can easily represent more than half the price of the ticket. And at worst, you could be out the entire ticket price. For that reason, you should seriously consider trip-cancellation insurance any time you have a lot of money up front:-- Regular travel insurance, bought separately, usually starts at around 5 percent of your total payments, but the price increases for older travelers - sharply for travelers over 70. That premium typically pays for a bundled policy including cancellation, medical, baggage and other coverages. SOURCE:SFGATE.COM