In its 2025 Air Hacks report, Expedia presents travelers with insights on the cheapest months and days to book flights, along with the optimal booking window for securing the best fares.

According to the report, one particular day of the week stands out as the most cost-effective for booking flights: Sunday. For the third consecutive year, Expedia has identified Sunday as the cheapest day to book airline tickets.

Travelers who book flights on a Sunday can save an average of 6% on domestic travel within the U.S. and up to 17% on international flights compared to bookings made on Mondays or Fridays.

When it comes to departure days, Thursday is the most affordable for international travel, offering an average 15% discount compared to flying on Sundays. For domestic U.S. flights, Saturday is cheaper than Sunday, allowing travelers to save 17% on average.

Expedia's research challenges the belief that summer is the most expensive travel season. Contrary to this common misconception, the report found that August is, on average, the cheapest month to fly, while February and March tend to be the most expensive.

For U.S. travel, flying in August rather than February can save travelers up to 12%. On international routes, flying in August instead of March can result in savings of up to 7%.

Another widespread assumption is that booking flights as early as possible guarantees the lowest fares. However, Expedia’s findings indicate that for domestic flights, booking one to three months in advance can save travelers up to 25% compared to last-minute bookings. For international flights, the most affordable prices are typically found 18 to 29 days before departure, rather than booking three or more months in advance.

The study also found that airfares are trending downward. Domestic flight prices have decreased by 1%, while international flights have seen a 4% drop compared to last year. Meanwhile, the price gap between premium and economy-class tickets has shrunk by 10% compared to 2019.

For those seeking to avoid peak travel crowds, Expedia recommends flying in quieter months like February, which experiences 65% fewer flights than the busiest travel month, July.

To reduce the risk of flight delays and cancellations, Expedia advises travelers to opt for morning departures, as these flights are significantly less likely to be canceled. Flights departing after 9 p.m. have a 57% higher chance of cancellation compared to earlier flights. The safest window to fly, in terms of cancellations, is between 9 a.m. and 3 p.m.