Volunteering to get bumped from a flight is an issue often raised by participants in the events on my book tour. As is the case with most situations I discuss in “Decoding Air Travel,” I advice travelers to think carefully before giving up their seat and examine the alternative ways to get to their destination — and to know exactly what they would get in exchange.

U.S. airlines, which overbook flights all the time, offer discount vouchers valued at as much as $400 for bumps on domestic flights, and up to $800 on international flights. Those certificates are very tempting and can save you lots of money. In fact, many travelers take certain trips only because they have vouchers to use. However, unless you are familiar with alternative flights that will get you to your destination, you may be asking for trouble…