According to Going's analysis, travelers want to look for the so-called Goldilocks Window (not too early, not too late) to get the cheapest airfare. For domestic flights, Keyes said that's one to three months in advance for off-peak trips and three to six months for peak-season travel, such as Christmas and New Year's.

For travel in December 2026, the optimal booking window (the "Goldilocks Window") depends on your destination. For domestic flights, you should aim to book 2 to 4 months in advance, meaning August or September. For international flights, the best deals usually appear 4 to 10 months ahead, so you should start monitoring prices as early as February or March. Because December is the most expensive travel month of the year, prices rarely drop "last minute." In fact, they typically surge 30–50% in the final three weeks of the year. In 2026, experts suggest using tools like Google Flights to track price trends and booking on a Tuesday or Wednesday for the lowest fare. If you see a round-trip international flight for under $600–$700 during the holidays, you should book it immediately.