You’ve finally sorted your holiday plans. Phew! Then, you go to book your flight and discover the price has gone sky high. Arrghh!

Who hasn’t known the hair-pulling frustration of paying more – or even worse, having to cancel your holiday plans altogether – simply because you left it too late.

The question is, how late is too late to avoid paying extra?

Global flight comparison site, Skyscanner has done some research into this question. Never mind if you missed out this summer, it’s knowledge you can store and take advantage of next time.

Using price data comparing fares paid by travellers on the same routes between 2016 and 2017, Skyscanner found 90 per cent of Australians missed out on a cheap domestic flight, and 75 per cent missed out on international flight bargains, because of booking at the wrong time.

Of the Aussies surveyed by Skyscanner, 42 per cent booked their domestic flight within two months of departure – in the timeframe when flight prices start to increase.

On average, the sweet spot for the biggest savings is booking 21-22 weeks in advance. But this can differ, depending on your destination and departure location.

Moreover, it’s not always convenient to book far ahead. Are the savings worth it?

According to Skyscanner’s data, savings average about 15 per cent, but up to 30 per cent off can be gained. Once again, this depends on the route.

For example, travellers booking 22 weeks ahead on Australia’s most travelled route (Sydney-Melbourne) knocked an average of 18 per cent off the standard price. Those booking the week before departure forked out 22 per cent more.

Flying from Sydney to Melbourne? Choose your booking time wisely. Photo: AAP

Don’t miss out on a Christmas holiday again

An online survey by Skyscanner found inflated fares prevented 41 per cent of intended travellers from booking a flight within the silly season.

However, its research found booking less than a week before departure was the main factor in travellers being faced with higher festive fares – up to 48 per cent higher.

By booking 18 weeks in advance, you can shave an average of 24 per cent off the average silly season fare. Put an alert in your calendar –  Skyscanner’s formula suggests you want to pencil in the week starting August 20.

Is there anything else you can do to minimise the cost of a fare?

Travel on a Monday in May

May is the cheapest time to hit the skies, according to Skyscanner’s research. Travelling in May can save you an average of 13 per cent. December (yeah, you guessed it) is the most expensive.

You can also save up to 14 per cent by travelling on a cheaper day, according to the Skyscanner report, Australia Travel Trends 2020. The amount of savings varies depending on your destination and departure location. But, in general, weekdays (except Friday – our most popular day to fly out) are the cheapest. No surprises there.

On average, Monday tends to favour the wallet most. For example, those who flew from Melbourne to Bali on a Monday saved 14 per cent over the Friday flyers.

However, if you’re departing from Sydney to Tokyo, Tuesday is more of a bargain, and if your destination is Auckland, try Thursday. Bear in mind though that, with savings between different weekdays sometimes on the slim side – hovering around only 4 per cent for many flight routes – it might not be worth stressing about.

Tuesdays are best for booking trips to Tokyo. Photo: Getty

Hop on the computer on Sunday

Oddly, the day you make your actual booking could also affect the price, according to the 2019 Travel Pricing Outlook (by Expedia and the US’s Airlines Reporting Corporation).

Their report found it was possible to save up to 36 per cent by making a booking on a Sunday. The most expensive days were Thursdays and Fridays. No explanation was given for the phenomenon.

Check out the sales

A Virgin Airlines Australia spokesperson advised that, along with booking in advance, travellers should look for cheaper flights in non-peak periods, such as outside the school holidays.

They also recommend signing up for alerts on discounted fares. Virgin has Happy Hour Sales every Thursday 4-11pm, monthly MatesRates or Early Bird fares, and Jetstar offers Friday Fare Frenzy (Fridays 4-8pm).