Andy Daniel thought he had found a terrific airfare from San Francisco to Miami for Christmas. Instead, he found a terrific disappointment.

When Daniel tried to book a $400 ticket advertised on Expedia, the price suddenly more than doubled.

“I called Expedia and a very polite, helpful agent apologized for the problem and found my $400 fare,” says Daniel, a microchip designer from Palo Alto, Calif. “She tried to book it for me — and then informed me that the fare had changed to $900 ‘because fares can change in seconds as tickets are purchased.’”

Right.

Bait-and-switch offers are one of the oldest — and popular — tricks in the travel trade’s book.

Maybe that’s one reason why customer ratings for online travel agencies such as Expedia are on the skids even as e-commerce companies as a whole are getting their highest marks in history. The authoritative American Customer Satisfaction Index earlier this year found that grades for the three major online travel sites dropped, with Expedia slipping almost four percent to a score of 75 out of 100 and Travelocity and Orbitz both receiving a 73.

That’s a low “C,” in case you were keeping track.

This isn’t limited to the three big online agencies, of course. Airlines, hotels and car rental companies have suffered similar declines in customer-service ratings. It would be unfair to pin this poor performance entirely on their slippery price displays. But it would be equally unfair to claim these fluctuating fares had nothing to do with it.

Travelers don’t trust their Web sites any farther than they can throw their desktop computers. Which isn’t very far.

I asked Expedia about its fare displays, and specifically about Daniel’s problem. Turns out the online agency has two systems that track airfare availability: one for shopping and one for booking. “While uncommon, the two systems will rarely return disparate fares, as appears to have happened in this case,” says Expedia spokeswoman Katie Deines. “It speaks to the highly dynamic nature of pricing and availability. Expedia works throughout the booking process to verify pricing and availability so we are showing customers the latest information.”

But travelers don’t care about the highly dynamic nature of pricing and availability. When they see a low fare one minute and a higher price the next, they call it a bait-and-switch. So do I. The price you’re quoted should be the price you pay. Every time.

Not everyone agrees with this simple assertion. One of my colleagues took me to task for referring to Delta Air Lines’ fare displays as a “bait-and-switch” a few weeks ago, claiming that it revealed my ignorance about the highly dynamic nature of pricing and availability.

I wish I was wrong about this, but I’m not. Calling these illegal sales tactics by their correct name reveals my indignation with the system — a system, I would add, that lot of so-called “experts” not only accept, but also defend, even as the customers whose interests they’re supposed to represent are foiled when they try to buy a ticket.

But wait. Aren’t travel companies — particularly online travel agencies — just victims of this scheme, like us? Not really, says Chris Lopinto, a partner for a site called ExpertFlyer.com that lets you connect directly to the computer reservations systems used by airlines. Without getting too technical, here’s what you need to know about how prices are set: Fares and rates are loaded into these reservations system and adjusted by the minute in order to maximize revenues for the travel companies. Companies use a team of math whizzes to predict demand and instruct the systems how to set the prices. Think of it as a game of “chicken” on a grand scale. And it’s played by nearly everyone in the business.

“The average person doesn’t understand what’s happening behind the scenes,” Lopinto told me.

We may never fully comprehend what’s commonly known as “yield management” in the travel industry, but there are a few ways of making sure you don’t become a victim of these deceptive pricing practices.

Always read the fine print
Beware of terms like “as low as” and “starting at” — as in “rates as low as $99” or “fares starting at just $49.” They’re almost always followed by “taxes not included”, “based on a roundtrip ticket” or “based on double accommodations” in four-point type on the bottom of the page. Perhaps the worst offenders today are airlines. They’ve begun a practice called “unbundling,” which is a sophisticated bait-and-switch tactic. By removing the cost of meals, luggage and advance reservations, they are making their prices seem artificially low. But when everything is added up, the ticket often costs much more than you expected. Incidentally, airlines love unbundling. In a recent earnings conference call, a Delta Air Lines executive declared, “a la carte pricing is where we need to go as an industry.” Do yourself a favor. Next time you hear the word “unbundling” just substitute the word “bait and switch.” It’s much easier that way.

Don’t count on a price until you have a confirmation
Most travelers believe a price quote from a travel company is like seeing a price tag on merchandise in the store. They couldn’t be more wrong. The price you see is almost never the price you actually pay, because at best, taxes, fees and surcharges are added to it. And at worst, the price changes between the time you get the quote and the time you click the “buy” button. Incidentally, why is it that you never hear of a fare going down during the reservation process? If prices are so highly dynamic, why can’t they be dynamic to the downside every now and then? Just something to think about. Bottom line: don’t count on a price until you have the confirmation e-mail and your credit card is charged.

Avoid the worst offenders
If you’re unsure about a travel company’s offer, you might want to consider what the Federal Trade Commission has to say about it. The government agency publishes an archive of case files going back to 1996 that could shed some light on the company you’re thinking of booking a trip with. Unfortunately, the worst offenders change their names, move and start another questionable business until they’re slapped with a “cease and desist” letter from the government. Another good place to look is your local Better Business Bureau which keeps files on businesses, including any recent complaints from consumers.

Use a travel agent
Competent travel advisers can spot a bait-and-switch offer from a mile away. It’s what they get paid to do. But not every agent is competent. Christine Austin, a homemaker in Louisville, Ky., swore off her travel agent after she fell for one of those “now-you-see-it/now-you-don’t” fares. “She called, told me the fare and ten minutes later called back and said the lower fare had disappeared while she was talking with me,” she remembers.

Since timing was important, Austin felt she had no choice but to buy the more expensive ticket. I think a good agent would have handled the situation differently — either by explaining that the first price was just a quote, and that prices could change, or by waiting until she was ready to buy before offering a price.

If it looks too good to be true, it probably is
Perhaps the easiest way to spot a bait-and-switch offer is to ask: Does this look too good to be true? If it is, then run, don’t walk. Reader Marianne Ventruella received one such offer in the mail last year that offered everything but the kitchen sink.

It included a travel voucher in the amount of $1,600, a cruise, resort visit and theme park tickets. She phoned the company and was connected to a salesman who insisted that she make an immediate purchase. “I knew it was a scam,” she says. Others aren’t so lucky.

I can’t cure the travel industry’s bait-and-switch epidemic in a single column. It takes concerted action by consumer groups, government regulators and fellow travelers like you.

But with just a little research, a skeptical attitude, steering clear of the worst companies and finding professional help, you won’t just minimize your frustration. You also won’t fall for the oldest trick in the book.