What's the best time to buy domestic airfare? Book on a Sunday, eight weeks before your flight, a new report says

 Sunday is the best day to buy airfare, according to a new study. 

Sunday is the best day to buy airfare, according to a new study. 

Sunday is the cheapest day to buy air travel, while the least expensive domestic tickets are sold an average of 57 days prior to departure, according to a new report. 

The data comes from Airlines Reporting Corp, an industry group that analyzed roughly 130 million ticket sales between January 2013 and July 2014. A wonky summary of the findings can be found on the company's website. 

But here's what you need to know:

Domestic travel

  • You'll find the cheapest fares an average of 57 days before your flight.
  • As a range, domestic fares are lowest 50 to 100 days prior to flight. During this period. fares fluctuate slightly, but they're essentially flat.
  • The median advanced purchase time for domestic travel is 20 days.
  • 24% of domestic travel is sold in the final week prior to departure.
  • Sunday is the best day to purchase domestic travel.
  • Monday and Friday are the worst days to purchase, likely because there is more "business travel activity."

International travel

  • The cheapest international fares are found 24 weeks in advance. The exact best date is 171 days prior to departure. 
  • Between 150 and 225 days before departure, you'll see only minor fluctuations in the cost of tickets. So booking on the "wrong" day probably won't lose you much money.
  • The average international ticket is sold 59 days in advance of travel.
  • Only 12% of international sales come in the final week.
  • Sunday is also the best day to buy international flights, with Monday and Friday being the worst days. 

The Wall Street Journal published a nice summary of the findings. Here is how Scott McCartney described the weekend phenomenon:

The lower Sunday and Saturday prices also result from the ability social media has given airlines to throw discounts in front of consumers at any time. That turns vacation shoppers surfing the Web on weekends into ticketed passengers without discounting tickets business travelers might buy while at work. And the findings reflect the lack of corporate sales over the weekend, since business travelers typically fly on more expensive tickets than vacation buyers.

UPDATE, Oct. 24, 2014: Brett Snyder, who writes the excellent Cranky Flier blog, says the media, including the Journal and yours truly, got this story partially wrong. Learn why here. 

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