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When to book a cheap flight: what actually works

There is no magic day to book a flight. You often read that you should buy on a Tuesday, or exactly so many weeks before departure. In reality, airlines adjust their fares continuously, flight by flight, depending on how full it is and on demand: no fixed rule holds for every route or every season. What works is knowing how to recognise a good price when it shows up, and being ready to decide quickly.

1. Know the usual price of your route

Without a reference point, you cannot tell whether a fare is good. For each route we follow closely, our travel tips pages give the median return price, the most common range and the cheapest departure month, calculated from our price checks over the last three months. A price well below the median deserves attention; a price within the usual range can wait.

2. Be flexible with your dates

Moving a departure by a day or two often changes the price more than the day you buy. School holidays, bank holidays and long weekends push demand up on most leisure routes. If you can leave midweek or outside the holidays, also look at the cheapest month shown on your route's page.

3. Look at nearby airports

From Brussels, Zaventem and Charleroi are not served by the same airlines or to the same destinations. Depending on where you live, a neighbouring airport may also be worth a look. Then count the trip to the airport in the price: a cheaper ticket from a distant airport may no longer be cheaper once the train or shuttle is paid for.

4. Compare the total price, not the headline price

Cabin bag, hold bag, seat choice: on low-cost airlines, these extras can change which of two tickets is cheaper. Our guide cabin baggage size and weight by airline sums up what each one includes. Also compare a return ticket with two one-way tickets, sometimes on two different airlines.

5. Book quickly when a really good price appears

A very low fare lasts from a few hours to a few days. When it matches your dates, check the conditions (baggage, times, exact airports) on the airline's or agency's website, then decide without waiting: the same price may not come back.

What our own alerts show

The 433 alerts sent by Tarmako since 30 September 2026 announced departures a median of 36 days after the alert was sent; half of them between 25 and 46 days (38 days for long-haul, 35 days for short-haul).

This is not a rule to follow: it is where our price checks found the biggest drops, and we only track departures in the coming months. These figures are recalculated each time the page is updated.

How Tarmako checks prices

Every two hours, Tarmako checks the price of each route it follows, based on recent flight searches recorded by our data provider. For each route, the “usual price” is the median of the prices seen per departure date over the last three months. An alert goes out when a recent fare falls well below that usual price. These are observed prices: they are neither guaranteed nor reserved, and a price may have changed between our check and your search. Our method in detail.

Leaving from Brussels? The page cheap flights from Brussels and Charleroi gives the usual price of each destination.

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Frequently asked questions

Is there a day of the week when flights are cheaper to book?

No fixed rule holds for every route. Airlines adjust their fares continuously based on how full each flight is and on demand. It is better to know the usual price of your route and decide quickly when a fare drops well below it.

How far in advance should I book?

It depends on the route and the season. Tarmako's alerts are most often for departures a few weeks away, but that is not a rule: it is where our price checks found the biggest drops, and we only track departures in the coming months.

Does Tarmako guarantee the prices it announces?

No. They are prices seen during our checks: they can change or disappear before you book. Tarmako sells no tickets; you book yourself with the airline or agency of your choice.