Readers of this blog will know that I'm somewhat down on airline frequent flyer programs, especially with all the new higher fees associated with them.

But depending on what kind of fare you earn with your miles, frequent flyer miles earned with a credit card can be astounding deals.

Case in point: I knew I needed to fly from New York to LA in February and wanted to fly in business class. I also wanted to try United's premium service, but the fare in business class was $2000 round-trip plus tax, way too high for my budget. So I looked into how many miles it would cost to upgrade. Turns out I only had a few hundred miles in my United MileagePlus account, but then I received a 30,000 mile bonus offer from United if I signed up for their credit card, precisely what I needed for an upgrade.

Shopping around for a United nonstop flight on my non-flexible dates of travel, I saw fares in the mid $500's with tax. But yesterday, the fare was just $399. So I first went to Expertflyer.com to see which flights had upgradeable seats and put a reservation on hold in economy, and then called United and asked them to ticket the economy fare and upgrade me, which they did in a few swift keystrokes (and they didn't charge a fee to speak to a real live human). Expert Flyer allows you to see which flights have upgradeable seats on dates of your choosing, and works with many but not all airlines. There is a monthly or annual fee for this service, but for many it's a small price to pay. The site also lets you see which airlines have award travel by flight and date and offers a lot of other neat features.

So my 30,000 miles (for which I'll end up paying only the annual fee for the United card) saved me $1600. That's what I call a bargain. I should point out that United allows you to upgrade from a much wider range of discounted fares than some other airlines, most notably Delta.