I recently wrote about the 10 Worst Rip-Offs in Travel, but 10 doesn't even begin to cover the full panoply of rip-offs across the entire travel space—especially the airline industry. Here's the basic principle of contemporary airline pricing: Rates are based on how much money the airlines think passengers will pay, not on the actual costs of doing business. Fares for connecting flights, for example, are often cheaper than fares for nonstop flights on the same route, despite the fact that nonstop flights cost airlines less to operate than connecting flights. This makes these gouges particularly painful. Here are my picks for the nine worst rip-offs in the airline industry.

Ticket-Change Fee

On most airlines, the cheapest tickets are nonrefundable. Originally, airlines meant that literally. No matter what happened, you didn't get your money back unless you could document a death or medical emergency. Soon, however, airlines found that travelers were getting so adept at "desktop forging" doctors' notes and funeral postings that the airlines changed the policy. Now, you still can't get your money back, but you can cancel your flight for a fee and use the remaining dollar value toward a future ticket.

The fee was originally $25 on most airlines; it was reasonable and consistent with the cost of processing the paperwork. But over the years, change fees have escalated to outrageous levels. On most major airlines, you pay around $200 to exchange a domestic ticket and $250 to exchange an international ticket. Often, these fees wipe out much of the ticket's remaining value. Consumer advocate Donald Pevsner was informed by a reliable inside source that the actual cost of the exchange to the airlines is now around $40. The rest is pure gouge.

Work-Around: A few airlines don't gouge you this badly. Southwest still doesn't charge a fee at all, and Air Canada, Alaska, Frontier, JetBlue, and Virgin America charge $100 or less. And for an extra $68, you can buy a Choice Essential ticket on American that waives any change fees and also gives you a no-cost checked bag.

Fuel Surcharges

If you thought that the Department of Transportation (DOT) rules requiring all-up price advertising ended the fuel-surcharge gouge, you're mistaken. Yes, in the U.S., airfare displays no longer break the true fares into separate but equally phony components, but some airlines—especially foreign ones—retain the distinction in their internal breakdowns and hit you with fees in these unexpected ways:

• They offer a "free" companion ticket that covers only the lowball, fake base fare and leaves you to pay the surcharge.
• Their exchange rules say that you can exchange the base fare but not the surcharge.
• They apply surcharges to "free" frequent-flyer award tickets.

This rip-off is especially noxious because it is based on a lie—that the fuel surcharge somehow isn't part of the regular fare. How bad it is? As of mid-October, British Airways was posting a round-trip from Boston to London with a base fare of $208, plus $230 in government/airport/security taxes and fees and a $458 "carrier imposed" (read: "fuel") surcharge. Ridiculous! If fuel costs were to go down from the present $3 or so per gallon to the 2002 level of 69 cents, do you really think that British Airways would charge only $208 for a round-trip to London? Feh!

Work-Around: Most U.S. airlines don't use the fuel-surcharge scam. Avoid the foreign lines that do.

Online-Booking Convenience Fees

Allegiant, Spirit, and several European low-fare airlines charge $10 and up to book a reservation online. The only way you can avoid this fee is to schlep out to an airport when an agent is on duty and buy there. Obviously, this system runs counter to true costs. Online bookings are by far the cheapest ways for airlines to sell tickets.

Work-Around: Sometimes you can avoid the charges by flying on another airline. But all too often, even with the fee, the low-fare airline will lock you in with either the lowest all-up cost or the best schedule option. Making a separate airport trip is a nonstarter for most, so you might have to put up with this gouge.

Online Seat-Assignment Fees

Quite a few airlines these days charge a fee, typically around $5 to $10, for you to preselect your seat. Again, as with booking fees, this runs counter to actual costs. Assigning seats online costs an airline virtually nothing; certainly less than taking up an agent's time when you're checking in at an airport.

Yes, we understand that airlines might want to reserve some of their "better" seats for folks on expensive tickets or exalted-level frequent flyers. But that, too, can be accommodated online. And couples and families who want to sit together shouldn't have to fret about seat assignments for days before their flights—and they shouldn't have to pay for a little peace of mind.

Work-Around: Your best bet—especially when traveling with a companion or group—is to check in early enough that the agent can find the seats you need before the plane gets full.

Co-Pays on Frequent-Flyer Upgrades

Many of you (and I'm with you!) have concluded that the best use of frequent-flyer miles is to upgrade a cheap economy ticket to first class (domestic) or business class (intercontinental). But these days, upgrades carry a stiff cash co-payment: On American, United, or US Airways, you'll pay each-way co-pays of as little as $25 (for a short trip on US Airways) but generally $75–$150 to upgrade a cheap domestic coach ticket, $125–$500 to upgrade a cheap ticket to Hawaii, and $300–$550 to upgrade a cheap economy ticket to Europe. (Delta doesn't post upgrade fees.)

When we first bought into the frequent-flyer deal, mileage-based upgrades were free. Co-payments are yet another instance of the airlines' devaluing miles even as they push us into chasing evermore miles with credit cards and other promotions.

Work-Around: On trips to Europe or Asia, the upgrade co-payments can get so high that buying a premium-economy ticket might look like a good alternative. Yes, you won't get the full business-class treatment, but you will get a comfortable seat and you'll save some miles.

Air Passenger Duty

This is one gouge even the airlines don't like—mainly because they don't get to keep any of it. The Air Passenger Duty (APD) applies to flights departing from U.K. airports. It was sold to the British public as a "green" incentive that would help alleviate the carbon pollution of air travel. The duty has escalated to a healthy hit on tourists returning from a British airport to the U.S. or Canada: £67 (about $107) in economy class, and double that in any higher classes, including premium economy. The duty also applies to award tickets. Rates are lower for flights within the U.K. and for short hops to Western Europe (£13) and higher to Asia and the South Pacific. Northern Ireland opted to reduce the duty to zero on direct flights to the U.S. or Canada.

Work-Around: On a multi-country trip, avoid returning from a U.K. airport if you can. Or consider ending your U.K. trip by taking easyJet to Amsterdam or Eurostar to Brussels or Paris and returning from there.

One-Way Coach Airfares

This one—submitted by a reader—applies to the common airline-pricing practice of pegging a round-trip fare (with a minimum-stay requirement) at a price that is often lower than the unrestricted one-way fares. The rationale is to hit business travelers—who want to get home over a weekend—while giving a price break to leisure travelers. It's a lot less prevalent now, because so many low-fare airlines set all one-way prices and force major carriers to compete, but you still see it on noncompetitive routes, especially those to or from hubs such as Atlanta, Charlotte, and Minneapolis.

Work-Around: Consider driving to or from a nearby airport with service by Southwest, JetBlue, AirTran, or some other low-fare airline that sells their lowest fares on a one-way basis. Or you can buy a cheap round-trip ticket and throw away the return fare. Or consider a hidden city ticket: Buy a ticket from a spoke city to another spoke city via the hub, then don't take the connecting flight. Both practices violate airline contracts of carriage, but airlines can't do much to enforce the rules.

Airport-Parking Rates

High airport-parking rates are another reader-nominated rip-off. And I agree: They can be very high. In Boston, for example, supposed "economy" rates are $27 for the first day, then $18 for the next six days, or $108 for six to seven days. Even my small hometown airport in Medford, Oregon, charges a high long-term rate of $9 per day. Rates don't have to be that high: At busy Charlotte Douglas International Airport, for example, the long-term rate is just $5 per day. But parking is one of the primary cash cows for big airports. Airports typically contract with private operators that, in effect, return more than 95 percent of the revenues to airport coffers.

Work-Around: You can avoid gouged parking rates in several ways:

• Leave your car home and take shuttles to and from the airport, or have someone transport you.
• Use private off-airport parking lots; you can find them around most big airports. Typically, however, they fine-tune their rates so as to be just enough below the airport's rates to generate the business they need.
• Many airport-area motels offer "park-sleep-fly" deals: Pay for one night and get "free" parking at the motel for as long as two weeks. You can take the night at either end of your trip. Rates are generally a few dollars higher than the motel's lowest, but this can still be a good deal.
• Fly from a nearby airport with lower rates. You can escape Boston's $18–$27 per day rates by flying from Manchester ($10 per day) or Providence ($60 per week).

Baggage Fees

Yes, the big-airline standard of $25 for one bag and $35 for a second bag can certainly add a lot to the real cost of what started out as a cheap ticket. I would be very surprised if the airline's actual cost of handling a checked bag were anywhere near that amount, so the fees very likely are a substantial overcharge. As with so many other fees, they're in the "because enough people are willing to pay it" class along with other so-called optional fees.

Work-Around: You have three main options: The most obvious is to avoid checking your bag, carry it on, and stuff it into the overhead bin. That doesn't always work, however. The bag may be too big or (more likely) the bin may be full by the time you get to your seat. Of course, you can pay extra to board early—substitute one gouge for another.

Southwest still doesn't charge for two checked bags and JetBlue doesn't charge for one, and both are good airlines to fly for other reasons as well. Additionally, some credit cards that are co-branded with airlines include no-charge checked bags on that particular airline.

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This article was originally published by SmarterTravel under the title Nine Worst Airline Rip-Offs.

Follow Ed Perkins on Google+ or email him at editor@smartertravel.com.