It is still possible to get an airline deal -- if you are lucky and ready to pounce.

Travel search site recently showed a round-trip ticket between Seattle and Cincinnati during the Christmas holiday for $318. The round-trip fare on Delta Air Lines was available for purchase from Alaska Airlines through its code-share agreement with Delta. Delta was selling the same ticket for $579.

The next day, Delta and Alaska's prices had jumped to $729 and $1,261, respectively.

What happened?

A code-share alliance allows one airline -- in this case, Alaska -- to market and sell another carrier's flights. Airlines have dozens of fares in place for the same flight, but usually just a few seats at the lowest price.

"Delta might have sold all the lowest-tier seats, and Alaska might have one or two left," said Delta's Trebor Banstetter. Airlines will coordinate to make sure their prices are aligned, but occasionally there are price disparities.

Part of the explanation for price differences has to do with what the airlines call "yield management," said Rick Seaney, CEO of, an airfare-search site.

Tinkering with dozens of "fare classes" (ticket prices set according to advance purchase requirements, minimum stays, flexibility to change, etc.), computers make a final decision on the seat price based on supply, demand and predicted trends.

"These models can and do change their minds at any time, which is one reason why you may get a different quote for the same flight at different times during the day," Seaney said.

Prices for airline tickets can rise and fall like a roller coaster; here are ways to land a ticket when prices are low.

Shop often and compare prices. Don't assume because you found the best deal one place that you'll find it there the next time. There is no one "best" place to buy.

Do your homework. Know what's a good price, either by relying on past experience or by tracking historical airfare data, using tools available on various websites.

FareCompare offers tips for deciding when and where to buy. predicts which way fares will go in the next three months, with "buy" or "wait" recommendations.

Sign up for e-mail fare alerts on sites such as Kayak, FareCompare or AirfareWatchdog for notices of price changes for flights on routes and dates you have in mind.

Be ready to move fast to grab a good fare. If need be, coordinate with your traveling companion ahead of time on dates and other logistics, so you can be ready to buy.

Know when not to buy. The general rule for domestic flights (international can be different), says Seaney, is that if you buy tickets more than three months out, you'll probably pay too much.