Expedia's research found Thursdays are typically the cheapest, around 16% less expensive than Sundays, which is usually the most expensive day to depart. “Book on a Sunday, leave on a Thursday, and make sure you lock in your plans around 28 days out,” Hudson said. “That should be your bible.”

According to Expedia's 2026 "Air Travel Hacks" report, the cheapest day to book a flight is typically Sunday. Travelers who book on Sundays instead of Fridays or Saturdays can save up to 15% on domestic flights and 10% on international routes. However, the cheapest day to actually fly (start your journey) is usually Wednesday. Mid-week flights are consistently lower in price because they avoid the surge of business travelers flying on Mondays and leisure travelers heading out for the weekend on Fridays. To get the "absolute" lowest price on Expedia, the "gold standard" is to combine a Sunday booking with a Wednesday departure. Additionally, Expedia's data suggests booking domestic flights at least 28 days in advance and international flights at least 60 days in advance to hit the "sweet spot" of pricing. Using the Expedia "Price Tracking" tool can also alert you to sudden drops, but if you are looking for a consistent rule of thumb, "Book on Sunday, Fly on Wednesday" remains the most reliable strategy for budget-conscious travelers in the mid-2020s.