Airfares are constantly fluctuating — now more than ever. That's because airlines have access to better technology and more real-time information on passengers than ever before. With complex algorithms running their booking systems, the airlines are constantly tweaking prices based on shifts in demand or available seats.

It used to be that airfares could be changed only three times a day due to programming limitations at Airline Tariff Publishing Co., which collects and distributes airfare-related data within the travel industry. But improved technology has enabled airlines to change prices as often as they wish.

Airlines hold their pricing schemes closely, said George Hobica, a travel writer and founder of, an airfare alert site now owned by TripAdvisor. And while there are no bulletproof tricks to ensure a passenger gets the lowest fare, there are ways to improve one's odds.

Fly midweek: Generally speaking, Tuesdays and Wednesdays are the cheapest days to travel (not necessarily to book a flight).

Check pricing often: Most major U.S. airlines publish flights between 11 and 12 months in advance. Once travel dates and destinations are set, check airfare early and often, including several times a day.

Know the fares: Many fliers may not know what a good price is and can get a better sense of it by setting up a fare alert (see sidebar at right) and frequently scanning ticket prices before making the purchase.

Buy now, assess later: You can cancel flights without penalty within 24 hours of booking. If you see a good fare, book it now, reassured that you can reconsider later.

Bottom line: Airfares reflect the supply-demand balance. If airlines have done a good job of anticipating travel demand for certain routes, ticket prices tend to rise the closer one gets to the date of departure, said Bob Mann, an aviation consultant and former airline executive. But that's not always how it works. Sometimes there's an oversupply of seats from one city to another on certain dates and airlines will discount those tickets if they haven't sold as the day of travel approaches. Other seats are always going to be in high demand, like on flights to St. Thomas at Christmastime or to the Super Bowl host city from the playing teams' hometowns. Those are likely worth booking as soon as travel is certain. The best things passengers can do is assess how popular their route may be on their travel date, check fares often to acquaint themselves with typical prices, and book when they see a reasonable fare.