The latest study by Expedia and the Airlines Reporting Corporation says that 2017 "could be a banner year for travelers taking to the skies."
"Based on billions of passenger flights from in 2016, the study concluded that the best day to buy airline tickets is Sunday, especially if you're booking more than 21 days in advance. In general, weekends are a good time to buy, but definitely not on Friday because of the increase in business travel bookings. Abide by these guidelines and you "can save more than 30 percent to Europe and 17 percent on travel domestically."
With that said, airlines change their fares multiple times a day, so you never really know. Last year, flights to Europe were at an all time low. This year? Look out for great deals to Africa thanks to burgeoning infrastructure and new airline routes.