How far ahead should you book to get low airfares?

The self-proclaimed "airfare geeks" at CheapAir.com have analyzed 560,611,868 domestic airfare searches from 2012 and have some interesting, if qualified, conclusions.

Their findings seek to answer every traveler's No. 1 question regarding airfares: How far in advance should I book to get the cheapest fare? And they do. Sort of.

The short answer: Seven weeks before takeoff. On average, fares bottomed out 49 days before the flight, then increased slightly, but remained steady until about a month out. After that, prices climbed as the travel date approached.

But too much advance planning isn't good for the bottom line, either. Though, not surprisingly, the highest fares, came with bookings made 11 or fewer days in advance, the next worst timing was 208, 209, and 210 days out, according to the analysis.

"For practical purposes, it's best to take this information as a guideline and not a rule," says CheapAir.com CEO Jeff Klee, noting that "a million caveats apply … For any given flight, the actual best time to buy might vary, depending on the market, the time of year, the day of week, and other factors."

Another interesting take away from the analysis: Purchasing a ticket on a particular day of the week (Tuesdays or Wednesdays, according to conventional wisdom) doesn't necessarily mean getting a lower fare. Yes, many airlines announce sales on those days, notes Klee, but there are enough unpublished sales on other days to offset any pattern.

For international flights, the lowest prices came 81 days out — or 11 to 12 weeks in advance.

As for peak travel periods like Thanksgiving, the analysis found the best time to buy was 96 days — almost 14 weeks — in advance.