Best airfare

A roundtrip from Philadelphia to Venice on Alitalia for $247? This offer, seen on Travelocity, seemed like a steal until our reporter discovered, just before booking, that taxes ballooned the price to $767. How about New York to Nashville on Frontier Airlines for $87? Great, but the outbound fare was available on only two dates, and our reporter couldn't find a comparable return fare within two months of departure.

Hidden fees, fine print, and blackout dates can make locking in a low price as tricky as a soft landing in turbulence. According to Rick Seaney, co-founder of FareCompare.com, which has analyzed price data based on millions of flights from hundreds of airlines and thousands of routes, the tips that follow can help you get a rock-bottom rate.

Check fares early. Start looking three and a half months before domestic flights, five and a half months before international. That's when the market begins to sort itself out and lower fares appear. Most airlines and travel sites make it easy to set up alerts to track fares.

Compare prices. Airline and third-party sites (Kayak, Expedia, Priceline, Travelocity) often list identical prices for flights, but they have different electronic reservation systems, and add and remove fares at different times. One system can trail another by up to 5 hours. Be sure to check the airline's own site, which may charge slightly less than third-party sites because there's no commission. Also, airlines offer frequent flyers upgrades, seats with extra leg room, and preferential boarding position.

Look beyond discount airlines. They might not be cheapest. "No carrier can afford to be even one dollar pricier than a competitor for a comparable flight at a comparable time," Seaney says, because it lowers placement in search-engine results, causing flights to be overlooked.

Buy at 3 p.m. EST on a Tuesday. That's quite precise, but Seaney says it's when the greatest number of cheap seats are available. Most sale fares kick in on Monday at 8 p.m.; by Thursday at 8 p.m., the sale period is over.

Be wary of weekends. Flights on Friday afternoon, Saturday, Sunday night, and Monday morning can be pricey because those times are popular with business travelers and vacationers.

Fly hungry. The least expensive flights tend to take off at dawn, around lunchtime, and after 6 p.m.

Consider a connecting flight. They can be substantially cheaper than nonstops, especially for international travel.

Shop for one seat. If you're traveling with a group, establish the base price for one passenger and compare it with the price for all. Reservation systems are programmed so that if there's one too few cheap seats for your group, all members get bumped up to the next price level.

Don't delay. You'll pay a premium if you book within 14 days of travel, and even more within seven days. Airlines would rather leave a seat empty than sell it at a steep discount.