You get what you pay for (sometimes)

Q. I was researching a fare on the American Airlines website, and found it was about $400 more than booking the same flights and dates on SmartFares.com or Momondo.com (two "discount" airfare sites). Do I risk not being able to earn miles on American Airlines if I buy from those sites? One of these websites only identifies the airline as a "Major Carrier", but it's the same flights as the American Airlines ones so I assume it's on American.

A. As grandpa used to say, you get what you pay for, and yes indeed, some airfare websites specialize in "consolidator" or "wholesale" airfare bargains that appear much cheaper than buying "retail." Here's the problem: sometimes these lower fares don't qualify for frequent flyer miles, advance seat selection and other perks. Worse, many of these fares are "you buy it you fly it"—in other words, no changes whatsoever, even if you're willing to pay a change fee. The ticket is only good for that flight and if you somehow miss it you might as well rip up the ticket. In addition, whereas sometimes if an airline cancels or delays your flight they'll attempt to put you on another airline, typically these cheaper tickets are good only on the original carrier. I'd contact any discount airfare site you're contemplating buying from and see what the hidden restrictions are.