How flexible dates help you find cheaper flights

In short: Flexible dates help because each flight is priced separately, so a nearby day can be much cheaper than your first choice. Searching a few days either side of your preferred dates gives you more chances to find a fare that meets your target.

Flexible dates help because every flight on every day is priced on its own. A flight one day earlier or later may have more seats left at a lower price level, less demand or a different mix of competing fares. If you can shift your departure or return by a day or two, you look at many more fares at once, and the cheapest of them is often lower than the fare on your first-choice date.

This guide explains why fares vary from day to day, how to decide how flexible you can be, and how to search flexibly without creating problems for the rest of your trip.

Why one day can cost more than the next

Airlines set prices per flight, based on how many seats have sold, how many they expect to sell and what competitors charge. Some common reasons a particular day is more expensive:

Popular travel days. Days when many people want to travel, such as the start and end of holidays or the days around a long weekend, often fill up faster.
Business demand. On routes used by business travellers, certain weekdays and times can be busier.
Events. Festivals, conferences and sports events can push up prices for the dates around them.
Schedule differences. Some days have fewer flights or no direct flight, which reduces choice.

None of these is fixed. The cheapest day changes by route and season, which is why checking a range of dates is more useful than following a rule about which weekday is cheapest.

Work out how flexible you really are

Before you search, be honest about what you can move.

Hard limits. Dates you cannot change, such as a wedding, a work start date or a booked event.
Soft preferences. Things you would like, such as leaving on a Friday, but could change for a good saving.
Knock-on costs. Leaving a day earlier might mean an extra hotel night, another day off work or extra pet care. A cheaper flight is only a saving if those costs do not eat it up.

A useful rule of thumb: decide how much a saving would need to be before you would change your dates. If moving by one day saves less than that, stick with your first choice.

Ways to be flexible

Date flexibility is the main lever, but there are others that work well together.

Shift the departure date. Moving by one to three days often changes the price.
Shift the return date. On return trips, the return leg can be the expensive part. Moving it alone may be enough.
Change the trip length. Staying a day longer or shorter changes which flight combinations are available.
Accept a stop. Flights with one connection are often cheaper than direct flights. Check that the connection time is comfortable.
Consider nearby airports. A different departure or arrival airport can make a difference, as long as getting there is not too costly.

Things to check before booking a different date

Arrival time. A cheap flight that lands late at night might mean an expensive taxi or an extra hotel night.
Connection length. Very short connections are risky. Very long ones are tiring.
Baggage and extras. Different flights and fares can have different baggage allowances.
Your other bookings. Make sure hotels, car hire and plans still line up.

Flexibility and price alerts work well together

A price alert with flexible dates watches several days at once. Instead of waiting for the fare on one specific day to fall, you are alerted when any day within your window reaches your target. That makes a hit more likely and saves you checking each date separately.

The trade-off is that the alert may find a fare on a date that is not your favourite. Only set a range you would genuinely be happy to fly.

How to set a Trigger for it

Go to flights and enter your route, trip type, cabin and passengers.
Pick your preferred dates, then choose a flexibility of 0, 1, 2 or 3 days either side. Choose the widest range you would actually book.
Set the maximum number of stops you will accept. Allowing one stop can open up cheaper options.
Enter a realistic target price. If you are not sure what to choose, see how to set a realistic target price.
Create the alert. Trigger re-checks regularly and emails you as soon as a fare in your date window is at or below your target, with a link to book on a trusted partner site, where you will see the live price.

Trigger is free, and you can have up to 10 active alerts. Each one ends on the departure date. Learn more in how flight price alerts work.