Who this is for: travelers planning an international trip two to nine months out who want a defensible booking window rather than a rule of thumb.
How we know: Sources are listed at the end. Every day count, month and dollar figure below is from a published study by Google, Hopper or Expedia, or from reporting that quotes one. Wildly records daily prices on about 240 routes; route pages show observed ranges as they accumulate, and this guide quotes none of them.
How far in advance to book international flights is a question three companies have answered with large datasets, and they do not fully agree. Google's analysis of fares observed from 2021 to 2025 puts the low point for international trips at 49 days or more before departure. Hopper's economists tell travelers to book three to seven months out depending on region. Expedia's 2026 report says the cheapest international bookings were made 31 to 45 days ahead. The differences come from what each dataset measures. Below is what each study actually says, a region-by-region synthesis, and the reasons a single number can mislead you.
What the three studies measured
Google. Google's September 2025 post analysed "average round trip airfares observed January 1, 2021 through August 1, 2025" on Google Flights. It reports the day count before departure at which prices were lowest, plus a "low price range" (Google blog):
- Domestic: lowest 39 days before departure (23 to 51 days is the low range).
- International: lowest "49 days or more" before departure.
- Europe: lowest "48 days or more" before departure.
- Mexico and the Caribbean: lowest 50 days before departure (26 to 79 days is the low range).
- Spring break trips in March or April: lowest 43 days before (28 to 61 days).
- Summer trips in July or August: lowest 21 days before (14 to 43 days).
- Christmas: lowest 51 days before (32 to 73 days). Thanksgiving: 35 days (24 to 59).
An earlier Google post from August 2023 said that for US to Europe, "average airfares from the U.S. to Europe only tend to increase over time, especially once you're about 10 weeks from departure", and put the best booking timing at 72 or more days out (Google blog). The two Google posts differ (72 versus 48 days for Europe) because they cover different years; that alone shows how much the "right" window moves.
Hopper. Hopper's January 2025 booking guide advises: "Start monitoring the price of your trip 7-8 months before departure" for long-haul trips; book Asia and Oceania "anywhere from 5-7 months before takeoff"; and book other international regions "3-6 months before departure to get the best prices". It also warns that prices "can increase by almost double in the last 3 weeks ahead of takeoff", a statement made about domestic flights (Hopper). Hopper's 2017 guidance was "at least 25 days in advance, but not further out than 150 days", with the note that "prices will typically soar in the three weeks leading up to departure" (Hopper). The Points Guy's September 2026 guide quotes Hopper's lead economist with the same five-to-seven-month figure for Asia and Oceania and three-to-six months for Europe (The Points Guy).
Expedia. Expedia's 2026 Air Hacks report, based on "bookings made on Expedia.com from December 2024 to November 2025", found international tickets bought "31-45 days ahead rather than more than six months out" saved "an average of $190", and domestic tickets bought 15 to 30 days out were "about $130 lower than booking 180+ days in advance". It named August "the most affordable month to fly overall, with fares averaging 29% cheaper than in December" (AOL, reporting Expedia's 2026 Air Hacks). Expedia's own newsroom page was rate-limited when we tried to load it, so we cite the AOL syndication.
Why they disagree
Hopper's windows are long because Hopper is telling you when to start watching, then book when its model says so. Google reports the day on which the average fare bottomed out. Expedia reports what its customers paid, and customers who book 31 to 45 days out include many flexible travelers who grabbed sales. None of the three is wrong; they answer three different questions. The practical reading is:
- Start watching early (Hopper's point).
- Expect the average low somewhere in the six-to-ten-week range for most international trips (Google's point).
- Do not assume that booking six months out is safer; on average it was not cheaper (Expedia's point).
Region by region
Europe. Google: low at 48 days or more (2025 data), 72 or more in the 2023 analysis, with fares rising from about 10 weeks out. Hopper: book three to six months out. Expedia: August was the cheapest international month across its bookings. For summer travel, the safer end of those ranges applies, because Google's separate finding for July and August trips (a low of only 21 days out) is dominated by domestic summer travel and should not be read as advice for peak transatlantic fares. Routes to watch: New York to London, Chicago to Rome, Newark to Lisbon. Our seasonality guide for the cheapest month to fly to Europe covers the calendar side.
Asia and Oceania. Hopper is the only study with an explicit figure: five to seven months before takeoff. Google's generic "49 days or more" applies as a floor. The gap between the two is large; the resolution is to start watching at Hopper's horizon and be ready to buy any time the fare hits a target you set in advance. Routes: Los Angeles to Tokyo, San Francisco to Sydney, and the Tokyo destination hub.
Mexico and the Caribbean. Google: low at 50 days before departure, with a wide low range of 26 to 79 days. Hopper adds that departures on Tuesday or Wednesday are cheapest for the Caribbean and Mexico. Routes: Miami to Cancun and the Cancun hub. Hurricane season and school calendars matter more here than the booking window; see the cheapest month to fly to the Caribbean.
Everywhere else (South America, Africa, Middle East, India). Hopper's "3-6 months" and Google's "49 days or more" are the only published anchors. Neither study breaks these regions out further.
Holidays override everything
Hopper's 2017 note stands: "For flights over July 4, Thanksgiving, Christmas and New Year, fares start high and they stay high." Google's Christmas figure (low at 51 days, range 32 to 73) is the closest thing to a published window for the winter holidays. If your dates are fixed to a holiday, the studies agree that waiting rarely pays.
How to use this without a crystal ball
- Pick the route and dates. Open the route page to see the lowest fare in the latest daily check and, where history exists, the typical/good/great bands. How those are produced is on /methodology.
- Decide a target price. A number at or below the route's "good" band, or below the fares you are seeing today, is a reasonable start.
- Set a Wildly alert at that target, with plus or minus 3 days if your dates allow, and turn on Google Flights tracking for the same search. Free plan details are on /pricing.
- When a fare hits the target inside the study windows above, buy it. Do not wait for the bottom; none of the three studies claims to identify it for a single route.
FAQ
Is booking six months ahead cheaper for international flights? Not on average, according to Expedia's 2026 report, which found tickets bought 31 to 45 days ahead cost about $190 less than tickets bought more than six months out. Hopper still recommends starting to watch prices seven to eight months out for long-haul trips.
What is the latest I can book without paying a premium? Hopper's guidance is that prices climb sharply in the final three weeks. Google's low ranges for international trips mostly end around four weeks before departure.
Is there a best day of the week to book? Google's 2025 analysis found Tuesday cheapest to book, but only 1.3 percent cheaper than Sunday, and concluded the day you fly matters more than the day you book. Expedia's 2026 report named Friday the cheapest day to book and fly.
Do these windows apply to business class? The studies above describe economy averages and do not break out premium cabins.
Sources
- Google blog: Holiday travel trends and insights for 2025: https://blog.google/products/search/holiday-travel-trends-2025/
- Google blog: 3 ways to find a great deal with Google Flights: https://blog.google/products/travel/google-flights-find-deals/
- Hopper: 2025 Travel Booking Hacks: https://media.hopper.com/research/2025-travel-booking-hacks
- Hopper: How far in advance should you book your flight?: https://media.hopper.com/articles/how-far-in-advance-should-you-book-your-flight
- Hopper: The cheapest time to fly internationally: https://media.hopper.com/articles/the-cheapest-time-to-fly-internationally
- AOL / Stacker: Travel hacks for 2026 (Expedia 2026 Air Hacks findings): https://www.aol.com/articles/travel-hacks-2026-data-backed-143518000.html
- The Points Guy: When to buy holiday flights in 2026-27: https://thepointsguy.com/airline/best-time-to-book-a-flight/