(Money Magazine) -- Bagging cheaper airfares depends not just on when you fly but also on when you shop.
On average, the best time to buy a ticket for non-holiday domestic travel is 49 days before departure, based on CheapAir.com's study of 560 million 2012 fare records; for international flights, 81 days is the sweet spot.
Beware of ticketing too far in advance: Seats bought about 200 days ahead are almost as costly as last-minute fares.
Beat the rush. When traveling around July 4 or another busy weekend, start looking early -- about 10 weeks beforehand in most cases, says CheapAir.com CEO Jeff Klee. For Thanksgiving, though, you might need a month more than that.
Seize the day. Shop on Tuesday afternoons, says FareCompare CEO Rick Seaney, since most domestic sales launch late Monday and are soon matched by rivals.
For non-vacation destinations, buy on a weekend; a Texas A&M study found that strategy resulted in average savings of 5%.
Check the numbers. For reassurance that your timing is right, take advantage of travel search engines' special features. Kayak.com's new Price Trend and Bing.travel.com's Price Predictor, fueled by fresh data, will forecast whether fares are headed up or down.