03/01/2013 07:16 am ET Updated May 01, 2013

Ask Airfarewatchdog: Airline Vouchers, Frequent Flier Miles Never 'Free'

Why is using airline vouchers so hard?

Q: On our return trip from Chicago my wife and I gave up our seats because the flight was oversold and we each received a $400 voucher for future travel. Can these vouchers be redeemed only at the United desk at an airport or can we do it online or on the phone? Do all major airlines have the same policies?

A: Not surprisingly perhaps, some airlines don't make it easy to use vouchers. United and American, for example, don't allow you to enter the voucher number on their websites and book travel that way. You either have to do it at an airport ticket counter (or city ticket office, but those are far and few between; AA only has three left). You can also buy your ticket on the phone and tell the agent that you have a voucher; you'll be asked to mail the voucher and the value of the voucher will be deducted from your fare once it's received. I recommend that you make a copy of the voucher. Delta, in contrast, allows you to apply the voucher's value online.

Whatever happened to "free" frequent flier tickets?

Q: I have saved lots of air miles on British Airways and American over the last 10 years by using my credit card. When I try to use them to fly to Europe or Africa, I noticed that BA charges $800 in taxes and fuel on a flight to Nairobi. Most of that is a fuel surcharge. American was only going to charge around $20 on a similar flight. I can buy a ticket for almost $1200 to Nairobi. So basically, my 100,000 air miles are worth $400. Also on British Airways, even when you try to find something almost eight months in advance, there is nothing available. I guess what I'm asking, is there anyone to complain to about these unfair fees or is it just shut up and save another airlines' air miles for years and then have them screw you too after you've saved 10 years to take your family somewhere exotic.

A: I never use my BA Avios points on economy class tickets, because it is indeed not worth it. You'll pay the same taxes and fuel charge on a business class ticket which would cost thousands more than an economy ticket. That's where the value is. And you're right, American, for whatever reason, does not stick you with the fuel surcharge. You can sometimes spend your BA miles on its OneWorld partner American and avoid the fuel charge, so that's one possibility. But if you're flying through London, you'll still end up paying the British government's air passenger duty, which keeps going up. It's usually best to attempt to use BA miles on a OneWorld partner on the phone rather than online, but you might also want to consult this article.