Departure board at Geneva Airport. Photo: Tiia Monto, Wikimedia Commons, CC BY-SA 3.0.
The best day to book flights is barely a thing. Google analysed years of its own flight data and found that Tuesday, the cheapest booking day, is only 1.3 percent cheaper than Sunday, the most expensive (Google, 2024). On a 500 dollar fare that is about 6 dollars. The myth survives because it is easy to repeat and impossible to disprove at the gate.
I believed the Tuesday rule for years. Then I tracked one route, Oslo to Lisbon, for three weeks straight and wrote the price down every morning. The cheapest morning was a Saturday. The next cheapest was a Thursday. The Tuesday I had been waiting for was the third most expensive day of the whole run.
Here is what actually changes what you pay, based on the data and on watching prices the boring way.
The best day to book flights, according to the data
There is no magic day of the week to book and save. Google's own data puts the gap between the cheapest and most expensive booking day at 1.3 percent. That is real, and it is too small to plan a trip around.
What that means in practice:
- Stop refreshing the booking page at midnight on a Tuesday.
- Stop screenshotting a "deal" because a blog told you Tuesday is cheap.
- The day-of-week lever is real but tiny. It is not worth planning around.
The reason the myth refuses to die: airlines repriced fares manually decades ago, often midweek, so Tuesday genuinely was cheaper in 2005. Pricing is now algorithmic and changes many times a day. The old rule describes a system that no longer exists.
Is there really a cheapest day to fly?
The cheapest day to fly is real, and it is different from the day you book. Flying on a low-demand day usually beats any booking trick. Google's data puts mid-week departures around 13 percent cheaper than weekend ones.
That gap is ten times bigger than the booking-day gap. Most leisure travelers leave Friday and come back Sunday, so the airline charges for the crowd. The pattern that holds across most routes:
- Cheapest to depart: Tuesday and Wednesday.
- Most expensive to depart: Friday and Sunday.
- Often overlooked: the first flight of the day. Early departures are less popular and frequently the lowest fare on the board.
On that Oslo to Lisbon run, shifting my outbound from Friday to Wednesday saved more than anything I did with the booking date. The flight itself was the same aircraft, the same route, one row back.
So the useful question is not "what is the cheapest day to fly." It is "can I move my trip by a day or two." If you can, that is where the saving lives.
The best time to book flights: how far ahead actually matters
The best time to book flights is a window, not a date. Book too early and you pay a premium for certainty. Book too late and you pay for desperation. The sweet spot sits in between.
Airfare studies broadly agree on the rough shape of it:
- Short-haul / domestic: roughly one to three months ahead.
- Long-haul / international: roughly two to six months ahead.
- Peak season (summer, Christmas, school holidays): add a month or two to both, because cheap seats sell out first.
This is also the real answer to "when to book flights" for most trips: early enough that the cheap fare buckets still have seats, late enough that you are not buying a year of price-protection you do not need.
One honest caveat. These are averages across thousands of routes. Your specific flight to a small airport in shoulder season will not read the textbook. Which is exactly why guessing the window beats nothing, and tracking the route beats guessing.
The 06:40 departure is usually the cheapest seat on the board. Photo: Lenny K Photography, Wikimedia Commons, CC BY 2.0.
The cheapest time to book flights is when you stop guessing
The cheapest time to book flights is the moment a route you are already watching drops below its normal range. Not a calendar date. A price you recognise as low because you have seen the high.
You only know a fare is good if you know what bad looks like. That takes a week of watching, not a clever rule. The habit that replaced every booking myth for me:
- Pick the route and the rough dates.
- Compare it across booking sites in one search, so you see the real spread instead of one airline's number.
- Watch it for five to seven days and note the range.
- Book when it sits near the bottom of that range, inside your booking window.
This is the whole reason Mondotickets exists. You put in one route and see live prices from hundreds of booking sites side by side, with no booking fees and no cookies quietly inflating the number you see. When the fare drops into the range you have been watching, you click out to the booking partner and you are done. The day of the week never enters the decision.
How I book a flight now
Here is the routine, stripped of every myth I used to follow.
- I decide where and roughly when. That is the only fixed part.
- I check whether I can move my departure to a Tuesday or Wednesday. Usually I can.
- I run the route through a comparison search and read the spread, not a single price.
- I watch it for about a week so I know the floor.
- I book inside the window: a month or two out for short-haul, a few months for long-haul.
- I never wait for a specific weekday. There is nothing to wait for.
The Lisbon ticket I finally bought was on a Wednesday departure, booked on a Saturday, about seven weeks ahead. None of that was a trick. It was just watching the price until I recognised a good one.
Frequently asked questions
Is there really a cheapest day to book flights?
Barely. Google found Tuesday is the cheapest booking day, but only by 1.3 percent over the most expensive day. That is a few dollars on a typical fare. The day-of-week booking rule is a leftover from manual fare-setting in the 2000s and is not worth planning around.
What is the cheapest day of the week to fly?
Tuesday and Wednesday departures are usually the cheapest, because most leisure travelers fly out Friday and return Sunday. Moving your departure mid-week saves more than any booking-date trick.
How far in advance should I book a flight?
Roughly one to three months ahead for short-haul, and two to six months for long-haul. Add a month or two for peak seasons like summer and Christmas, when the cheapest seats sell out first.
Do flight prices drop at the last minute?
Rarely, and not reliably. Last-minute fares can fall on routes with empty seats, but airlines usually raise prices as departure nears. Waiting for a last-minute drop is a gamble, not a strategy.
What is the actual best time to book flights?
The moment a route you have been watching drops near the low end of its normal range, inside your booking window. You learn that range by comparing prices across sites for about a week before you buy.
Compare flights, hotels, car hire, and airport taxis across hundreds of booking sites in one search at Mondotickets. No booking fees, no price-inflating cookies. We do not sell tickets; we show you live prices and send you to the booking partner. See how we earn on our How we earn page.
Sources:
- Google, "How to find the best deal on your next flight" (1.3 percent booking-day gap; ~13 percent mid-week vs weekend; booking-window data): https://blog.google/products/travel/how-to-find-the-best-deal-on-your-next-flight/
- Google's data puts the lowest domestic fares around 23 to 51 days before departure, and international around 49 days or more. The one-to-three-month and two-to-six-month ranges above are rounded for planning, not guarantees.
Claude AI helped me with phrasing and proofreading in this article.
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