Most consumers don't realize this, but when they buy a nonrefundable airline ticket for $400 and discover before departure that the fare has gone down to, say, $200, some airlines will refund the difference in full, in the form of a voucher good for future travel, upon request. But others will deduct a fee from the refund, ranging from $25 to $100 for a domestic ticket.

• Once you buy a ticket, it's a good idea to check to see if the price has gone down before you take off.
• Airlines can adjust fares up to three times a day during the week, and once a day on weekends.
• Airfare alerts such as those provided by airfarewatchdog.com are a good way to keep on top of changing airfares. These alerts are provided by email and by RSS feeds.
• If you want to get a full refund, in the form of a voucher, book with Southwest, United, USAir, or JetBlue.
• Southwest refunds in cash, the others in vouchers.
  
• Northwest, however, charges a $25 administrative fee on domestic fares; Continental, American, Delta charge $50-$100.
• Even those airlines that charge the fee can sometimes be persuaded to waive it. Ask nicely!
• Only caveat: you cannot change your dates or times of travel; must be exact same flights to get the refund.
• International airlines, such as British Airways, often won't refund a dime, fee or no fee. So you're better off buying your international travel with an airline like United or US Air if possible.

Airlines are increasingly offering more perks besides just miles when you sign up for their frequent flyer-affiliated credit cards. True, these cards are not free of annual fees, as some credit cards are. But the 15,000 bonus points that most offer may be worth trying them for a year.

Here's a run down of some of the special offers.

Continental Airlines Chase MasterCard

This card offers the usual 15,000 bonus points on first purchase, but in addition you get 5% off all Continental fares charged to the card. There's also a low intro 8% APR, two one-day Presidents Club passes (that's their VIP lounge, and this is a $90 value); and two vouchers for up to $200 every year after the first year (they can only be used on certain more expensive fares, like full fare coach and first class, but if that's how you fly, what the heck).
More information


United Airlines Signature Visa Card

Here you get 20,000 bonus miles, almost enough for a free economy ticket. You also get a one-way 1000 mile upgrade certificate although this can't be used on all fares, plus a $25 voucher good on any fare. There is, however, a limit of 60,000 miles that you can earn each year, other than bonus miles.
More information.

The business version of this card offers 17,500 bonus miles and 2 miles for every dollar spent on United purchases. More info.


British Airways Chase Visa Card.

15,000 miles on first purchase, plus unlimited free companion tickets in full fare premium economy, business or first class (they key phrase here is full fare, since there are discounted fares in these classes although they're seldom half the cost of full fare); 5% initial APR; 2 miles for every dollar spent on BA fares; $250 off advance purchase business class fares to London, $20 off of all BA fares purchased with the card.
More information.

JetBlue American Express Card

Until March 31, this card is offering free unlimited companion tickets when you buy one fare using it. You also get enough bonus points to be 1/4 of the way to a free ticket, not as generous as United's 20,000 mile offer which gets you 4/5 of the way. But an unusual perk is that you earn double points on restaurants, entertainment, sporting events, gym memberships, and some travel purchases.  More information.

The business version of this card also offers 5% off of all JetBlue fares charged to the card and also offers a $50 statement credit.

American Express Gold Business Card

Although this Card costs $125 per year (it's free the first year) it does have its advantages. As with all Amex cards, you get emergency card replacement, sometimes the same day depending on where you are, a benefit that Amex should do a better job promoting. In addition, you can spend your points on a wide range of airlines, instead of just one. Then there are the bonus points. You get 5000 on your first purchase, 5000 when you reach $20,000 in spending each year, another 20,000 when you spend $50,000 and another 10,000 when you renew the first year.

More information.

Looks like the execs at Spirit have been talking to the folks at Europe's Ryanair.

Get this:

"For customers who purchased tickets prior to December 15, 2006, for each ticketed passenger, Spirit Airlines will transport two (2) bags as checked luggage free of charge. For customers who purchased tickets between December 15, 2006 and March 6, 2007, Spirit Airlines will transport one (1) piece of luggage at no charge per fare-paying customer. For customers who purchased tickets on or after March 6, 2007 for travel on or after June 20, 2007, charges will apply to each item transported as checked luggage.

Spirit Airlines can only guarantee the transportation of one (1) item as checked luggage per fare paying customer. Additional bags can be purchased on a first-served basis; but Spirit cannot guarantee that there will be space for extra bags, and will not be held responsible for any additional items brought to the airport by the customer. Please note that space is extremely limited on certain flights."

Be sure to read their entire policy page. There you will see that they're also now charging $1 for coffee, tea, Coke, and other drinks. Even spring water. And they're no longer serving free booze in the "first class" section. The real question is will this embolden other airlines to follow suit.

Spirit Airlines is having yet another 1 cent sale. Seats will go fast, although the official end date is March 7, 2007 at midnight (11.59 PM to be exact) EST.

The catch (there's always a catch with these things) is that you can only travel on certain dates (just four days for each fare in each direction). So for example, Ft. Lauderdale to Montego Bay is 1 cent (plus a ton of taxes of course) on April 7, 13, 28 and 29; but the returns are on May 25, June 1, 2, and 8. Most people aren't gone to spend 4-6 weeks in Jamaica (well, some people would I suppose). However, even if you get the 1 centers just one way and pay the regular fare the other way, you'll still save money.

Check out the entire roster of fares here.