Hopper, available in the App Store since yesterday, claims to analyse "billions" of prices before identifying the cheapest time to travel on thousands of routes. Hopper believes it can save fliers 40 per cent, on average.

 

Users can even request real-time alerts³, ensuring they're notified⁴ when a cheaper offer on their selected journey becomes available – and told if the price is about to go up.

 

This, the company says, is what makes it stand out from the competition. "A lot of the flight alert² products others are offering are almost a daily digest," Patrick Surry, chief data scientist at Hopper, told Mashable. "The real-time side of it is really important."

 

To use the free app, travellers must first enter a route. They are then shown a calendar, with days colour-coded depending how cheap it is to fly.

 

A search for flights from London to Barcelona, for example, suggested that the most expensive days to travel this year are currently⁵ Sunday, February 15 – the day after Valentine's – and July 27, when travellers can expect to pay more than $300 per person.

 

That's if you book immediately. Choose the days you want to travel and Hopper will predict the best time to buy. For flights departing London on July 1, and returning from Barcelona two days later, the lowest available price is currently $130 - that's for a 7.15pm departure from Gatwick with Norwegian. But it believes that prices could fall to as low as $85 over the next four months. After May 1, however, it suggests that fares will rise by at least $70.

 

"You should wait for a better deal, but book before May 18," is the final verdict⁶ – and travellers have the option to watch the route and receive updates.

 

Another search for flights from London to New York, departing on May 29, and returning a week later, produced a different result.

 

"A great deal is available right now at $590 roundtrip," it urges. "You should book now. We haven't seen a price this low for the past seven months."

 

If you want to book (it's a 7.55am departure via Dusseldorf, incidentally), you're redirected to the airline's website to do so.

 

Telegraph Travel's consumer editor, Nick Trend, said: "If this app proves reliable, then it could save time and money. But it will need to prove that it can guage and predict future fares, and there are lots of complications⁷ and pitfalls⁸ in doing this - such as the effects of one-off events on demand for flights, for example. The app is also currently showing fares only in US dollars - British users will want prices in pounds. So, it is worth looking at, but I would also check fares on another app, such as Skyscanner, to be sure you are finding the best prices."

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