Of all the world’s everyday mysteries — like why washing machines eat socks — few are more frustrating than fluctuating flight prices. One day it’s a deal, the next it’s double. But why do prices change so much, and when is the best time to book a flight?

Unlike the missing socks, this one we can explain.

How do airlines price tickets and when are flights cheapest?

Prices fluctuate constantly. Drops often happen when demand is low, after cancellations, or during sales.

Airlines want planes full, but they also need to turn a profit.

Pricing is driven by:

• Traveler type: Routes with more business travelers may start cheap to attract early bookings, then spike closer to departure when business flyers tend to book.

• How full the flight is: If bookings are slow, prices may drop to fill seats. Later, last-minute fares rise to capture those who must travel.

• Real-time data: Airlines use algorithms that react instantly to cancellations and new bookings. A few cancellations could trigger a sudden price drop.

How far in advance should I book for the best price?

Booking early can save you money, but how early depends on your route.

There’s no magic number, but previous pricing trends suggest that booking 1-3 months ahead for domestic flights and 2-6 months for international routes may offer better prices. That said, it depends heavily on the route and season.

For more guidance, check out the Skyscanner Savings Generator to find when is the best time to book a flight for your route.

What days of the week are flights cheaper?

Earlier in the week tends to be better, but not always.

Our analysis has shown that flight prices often follow a weekly cycle. Typically, the lowest fares appear earlier in the week, while higher prices are more common toward the weekend. This is why the answer to “When do flight prices go down?” is sometimes… a Tuesday.

What is the cheapest month to fly?

This one doesn't have an easy answer because it varies by route. The cheapest month to fly will depend on destination, seasonality, and demand. However, flight search tools can help you find out. For example, use our Cheapest Month search filter to quickly spot the best-value months and days to fly.

How do I know when flight prices drop?

You don’t have to check every day — we’ll tell you.

If you’ve got your eye on a destination, the easiest way to catch a price drop is to set up a Skyscanner Price Alert. Our tools monitor real-time flight prices and notify you as soon as they go up or down.

That way, you can book at the right time, without the guesswork.

Do flights get cheaper closer to departure?

Sometimes, but last-minute deals aren’t guaranteed. Price drops are more likely on less-busy routes or off-peak travel dates. On popular routes, prices often rise as departure nears.

Keep an eye on our flights page for last-minute flight deals. If a destination you've been curious about comes up, or if you're flexible about where to travel to, you can bag a bargain.

Extra ways to find cheap flights

Smart traveler tools to help you save even more

• Skyscanner doesn’t raise prices based on searches. No cookies or tracking tricks — just honest pricing.

• Not sure where to go? Select “Everywhere” as your destination to uncover the cheapest options from your departure airport.

• Watch for airline sales. Some airlines run seasonal deals with limited seat availability — book fast if you spot one.

• Flex is your friend. If your travel dates aren’t fixed, use flexible date filters to explore a wider range of savings.

• Check out the Skyscanner Savings Generator to find the best time to book flights for your route.

Final thoughts: When is best to book flights?

With the right tools and timing, you can book smarter and travel better. Whether you're planning ahead or holding out for a deal, Skyscanner helps you find the right time to book. Ready to catch the best fare? Use Price Alerts, Whole Month search, and the Cheapest Month filter to stay in control of your travel budget and make your next trip happen for less.