Lufthansa SunsetWe get this question a lot. Truthfully it’s a tough question to answer. We’ve witnessed wild price swings for the same exact flights by a couple of hundred dollars within the same day. Generally speaking though, the further out you can buy your tickets the more you’ll save. But not always.

Thankfully, the Airline Reporting Corporation (ARC) has recently done a study that should benefit us all. After looking at all air tickets purchased during an 18 month survey between 2013 & 2014 they discovered Sunday as the best day to purchase plane tickets. Savings can be as much as 13% domestically and 31% internationally over buying the same tickets on Tuesday.

“This latest study by ARC is significant because it reveals that not only have the lowest airfares shifted from six to eight weeks out for domestic travel, but the savings are markedly greater on a percentage basis,” said Chuck Thackston, managing director of enterprise information management at ARC. “It was also interesting to see that the data showed the least expensive tickets were purchased on a Sunday as opposed to Tuesday, which is a common belief.”

The best domestic fares were found by buying your tickets at least 8 weeks before departure. What’s interesting is the lead time for buying tickets increased by 2 weeks over a similar study in 2011. For international fares the best savings came from buying tickets at least 24 weeks (6 months) prior to departure.

While you may get the best fares on Sunday, tickets purchased on Saturday also offered a significant savings over buying the tickets on Tuesday by nearly 11% domestically and 28% internationally. That’s not to say you might find isolated last minute cheap fares, but the averages favor buying as far out a possible.

So when should you purchase your plane tickets? As soon as you can.