Is there really a 'cheapest' time to book a flight?

This week, the price comparison site kayak.co.uk released data revealing the best time to book your flight in order to get the cheapest fare. It covered some of the most popular destinations in Europe and several long-haul routes for travel in each of the four seasons, based on historical searches for fares on its website.

The Kayak survey revealed some impressive-sounding savings – more than 60 per cent on some long-haul routes, depending on how far ahead tickets were booked. And it did a good job in presenting its research in a coherent way. Not only did it advise how far in advance to book, it even gave details of the hour of the day when you might get the best price. It also indicated the days of the week when it is cheapest to fly to each destination at each time of year.

But while it threw up some potentially useful guidance, there are some fundamental problems with using data like this.

First, what was true last year may not be true this year. Holiday dates – especially Easter – change. New airlines start up. Other airlines add routes or drop them. International events – like terror attacks or the migrant crisis – can skew the figures massively, not just for the destinations directly affected, but for those that people choose to fly to instead. A wet British summer can bring a rush of late bookings to the Med and hence higher fares; a dry one can lead to a dearth and hence price reductions at the last minute.

Second, while the potential savings highlighted by Kayak sound impressive, they represent the difference between extremes. If you compare the highest possible cost with the lowest possible cost, you are always going to make savings look good.

In reality, most seats are sold at prices which are substantially moderated from those extremes. In fact, would anyone who paid the highest fare actually have been able to book at the cheapest price if they had only done their research properly?

Lastly, we are dealing with averages which don't always apply to the specific. It may be that for flights to Tenerife in autumn, fares were lowest on Wednesdays. But for the specific week you are thinking of travelling this year, Tuesday might be cheapest.

So what can we learn from this research? I think it is mostly of academic interest and it would actually be quite complex and pretty hard work to apply it as part of your booking strategy. A case, perhaps, of too much information.

If it has a value it is because, broadly speaking, it confirms what we already know. So you don't need to pore over all the figures. Stick to the principles listed below and, while you won't always pay the lowest possible fare, you can be pretty sure of getting a reasonable one: