Q. What are my rights if a piece of checked airline baggage goes missing?

A. It depends on what you mean by missing, and whether the flight is domestic or not. If the bag is lost forever on a domestic U.S. flight, then you can claim up to $3300 in compensation from the airline, but you'll have to produce receipts for the value of the bag and its contents, which is why I advise readers to save every receipt for clothing purchased. Note that "valuables" such as electronics, jewelry, antiques, cash and other similar items will not be covered by the airline (these should always go in your cabin luggage), and the airline will attempt to depreciate the value of your possessions, just as an insurance company would in the event of a loss. The rules are different for checked baggage lost on flights originating or flying to non-U.S. destinations.  Many countries and thus airlines follow a set of rules called the Warsaw Convention, which limits liability for loss or damage to luggage at  $9.07 per pound ($20.00 per kilo) for checked baggage with a maximum of $640, and $400 per passenger for unchecked baggage, unless a higher value is declared in advance and additional charges are paid. Most  travel, however, will be governed by the newer "Montreal Convention," which stipulates higher liability limits for international flights (but it's still less than domestic liability). That’s why it’s so important to buy excess valuation coverage,where available, when checking bags on an international flight. Ask about this coverage when you hand over your luggage at the airport. It's surprisingly inexpensive, ranging from 50 cents to one or two dollars per $100 of coverage. If your bag is merely "delayed" rather than totally lost, however, things get murkier. If you can prove consequential damages, the airline is still liable up to the amount stipulated above, but such damages may be difficult to substantiate. For example, if your business suit was in the delayed luggage and you were scheduled to speak at an important conference the next day but were traveling in your gym clothes, you could justifiably buy a new suit and attempt to charge the airline. However, you wouldn't want to buy a $3000 suit. Reasonable behavior is advised in such circumstances.

Q. I purchased a ticket online on American Airlines' website. I received an email confirmation from American showing that the travel dates were correct but upon but upon further examination after the fact noticed there was not ticket number or record locator on it. The day before travel, I attempted to check in online but was informed that the reservation had been canceled. American said my credit card number had been rejected three times by American Express. They also said they sent me an email informing me of the rejection, but I never received it. I immediately called Amex and was told that there was no record of American attempting to charge my credit card. I had to buy a last minute fare that cost me well over $1000 more than what the original fare cost. Do I have any recourse and what should I have done differently.

A. I've never heard of something like this happening, and I doubt there's any legal recourse if you read the fine print terms of service on AA's website. It sounds like there was a computer glitch of some kind. It's possible that American's attempt to notify you of the credit card problem but it went into your spam folder. The only thing you could have done differently was to check your credit card statement online soon after purchasing your fare to make sure that the charge went through, so I advise everyone who makes a reservation online to do this. In fact, it's a really good idea to check your recent credit card charges online every day to make sure there were no fraudulent charges posted to your account.

Q. I've never been able to find an airfare website that allows me to enter specific dates that I'm available to travel, such as leaving Nov. 12 and returning Nov. 18, and then shows me a list of the cheapest fares to anywhere leaving from an airport I specify. There are sites that show the lowest fares to various destinations from my local airport, but not according to the exact dates I specify. Why is that?

A. I've received many requests here at Airfarewatchdog for just such a website. The only reason I can think of that one doesn't exist is that it would take a huge amount of computer processing power. If you've ever waited for an airfare result between specific cities on specific dates on sites like Orbitz, imagine how long it would be to sort out an up-to-the-minute list of fares between every possible city pair on every possible combination of dates. I'm no math whiz, but the number of iterations would be enormous. Maybe some computer genius reading this will figure out how to do it.

Q. I recently checked into booking a mileage ticket on United. It seems that United is constantly sending me opportunities to "spend" the thousands of miles I've accumulated. To my surprise, a $50 fee was added because one of the flights was booked fewer than 21 days out. When did this happen? I have been at the "Premier Exec" level in United's frequent flyer program for many years, dropping to "Premier" this year. At this point, it seems it's little to no advantage to spend my travel dollars with United, let alone any other airline, out of loyalty.

A. United added (well actually, reinstated) this close-in booking fee -which they had previously eliminated- on June 15, 2011. The reason given was to align United's policy with Continental's and provide consistency between the two airlines. On the plus side, United reduced the fee for changing your routing or destination on a free ticket from $150 to $75. A number of airlines charge this fee presently, including American, US Airways and Virgin America. Southwest does not. For a look at frequent flyer fees, including those for using miles to upgrade seats from economy to business and first class, have a look at our fee chart.

Q. I’d like to book a ticket from Tampa to Hong Kong with a stopover in Los Angeles on the way out. What’s the easiest and cheapest way to buy such an airfare on the internet?

A. Some airlines sell stopovers at very reasonable fares, depending on the route. Rather than buying a multi-city fare online, I’d do it by calling the airline’s reservation department, or by calling a travel agent. In your case, you could also buy one fare round-trip from Tampa to Los Angeles and a second round-trip fare from Los Angeles to Bangkok. You might even find that this is the cheapest option, but make sure to leave enough connecting time between flights on the inbound return trip.