Why this guide: about 1,900 people a month search Google for “cheapest time to book flights” (US, DataForSEO Labs, September 2026). This is the answer we would give a client, written to be booked from.
The short answer
- Book domestic1–3 months ahead; the lowest fares cluster 3–6 weeks out for most routes
- Book international2–8 months ahead depending on season; 4–6 months for summer and Christmas; last-minute is almost never cheaper
- Fly onTuesday, Wednesday and Saturday; avoid Friday and Sunday; early morning and late evening flights are cheaper than mid-day
The booking window
Airlines open fares 11 months out at a moderate price, drift for months, then move: fares drop into a 'prime booking window' as the airline fills the cheap fare classes, and rise sharply in the last three weeks as business travellers book. Google Flights' and Expedia's published analyses put the domestic sweet spot at 1–3 months (about 38 days on average), international at 2–8 months (earlier for peak season, later for shoulder), and the Christmas and summer peaks at 4–6 months. Within 21 days of departure, prices go up on almost every route.
The Tuesday myth and the days to fly
The day you book barely matters — airline pricing is algorithmic and continuous; 'Tuesday at 3 p.m.' was true when fares were filed in batches and has not been for a decade. The day you fly matters a lot: Tuesday, Wednesday and Saturday departures are consistently the cheapest (business travellers fly Monday and Friday, leisure travellers Friday and Sunday), by 10–20% on many routes. The first flight of the day and the last are cheaper than the 10 a.m.–4 p.m. block.
Season, route and flexibility
Shoulder seasons — see our best time to visit guides — cut fares 20–40% versus peak. Flying into a secondary airport (Newark instead of JFK, Gatwick instead of Heathrow, Beauvais instead of CDG if you must) can be cheaper but factor the transfer. A day's flexibility either side opens the calendar view: the engine's flights search shows a fare grid across dates, and the cheapest combination is rarely the one you first typed. Positioning flights (flying to a hub to catch a cheap long-haul) can save hundreds on transatlantic and transpacific fares.
Alerts, points and mistakes
Set fare alerts on the route and dates once you are inside the window; book when the price falls into the lower third of what you have seen — waiting for the absolute bottom usually loses. Points transfer partners (Chase, Amex, Capital One to airline programmes) often beat cash in business class and on peak dates. Mistake fares and flash sales are real but rare; follow the deal newsletters and be ready to book within hours. Never book the cheapest fare without checking the bag and seat fees — basic economy on a transatlantic can cost more than main cabin once bags are added.
Booking it
The engine's flights page has flexible-date search, cabin filters and the fare calendar; bookings made through it can be paired with hotels in Vacation Packages, which sometimes prices the flight lower than standalone. Book, then set the chauffeur for both ends with the flight number — the driver tracks delays. See our red-eye, layover and carry-on guides for making the cheap fare comfortable.
Three things to get right
- Domestic 1–3 months out; international 2–8; holidays 4–6.
- Fly Tuesday, Wednesday or Saturday; the first or last flight of the day.
- Book when the fare is in the lower third of what you have seen — don't wait for the bottom.
