Aviation CheapAir analyzes best time to buy airfares for 8,000 routes By Robert Silk / February 25, 2016 Share 1 -- CheapAir.com introduced a new feature that allows shoppers to see the prime booking window for approximately 8,000 airline routes. The feature, part of CheapAir’s “When to Buy Flights” page, is based on the website’s analysis of 1.3 billion airfares in 2015. The tool went live in conjunction with CheapAir’s release Thursday of its 2015 airfare study. The website found that on average, the best time to buy a domestic flight is 54 days in advance. But because every trip is different, CheapAir also has, for the first time, designated broader booking windows, with what it calls the Prime Booking Window falling between 21 and 112 days of a trip. “This is the zone for bargain hunters,” CheapAir said. “During these 90 days, fares fluctuate a lot, sometimes day to day. Travelers are urged to check prices frequently during this period and to buy when a bargain pops up.”The company laid out four other zones, with the "First Dibs" zone (197 to 335 days out) joining the "Hail Mary" zone (0 to 13 days out) as the most expensive. Tickets bought during he "Peace of Mind" zone (113 to 196 days out) typically cost $20 more than during the "Prime Booking Window." Tickets purchased during the "Push Your Luck" period (14 to 20 days before a flight) vary dramatically. Though great deals are sometimes available, airfares are typically higher than they are during the Prime Booking Window. The prime booking period, though, varies from route to route. For example, the best time to purchase a round-trip from Atlanta to Los Angeles is between 93 and 25 days before a flight, CheapAir’s new tool shows. In contrast, the sweet spot for purchasing plane tickets between Detroit and Miami is a much narrower 64 to 38 days before the trip.