The secret to finding cheap flights – and the truth about mistake fares

Jack Sheldon reckons he can save each of his 200,000 subscribers around £400.

That works out at a potential £80m kept in the pockets of travellers thanks to emails in their inbox from Jack’s Flight Club.

“Each email has one deal as most of them do not last very long, sometimes just hours,” says the 29 year-old, who focuses his attention on flights leaving the UK and Ireland but is based in Kiev.

How does he do it? A computer program scours every fare on every route by every airline waiting for the cost of a seat to fall - usually thanks to an unannounced flash sale or a “mistake fare”.

London to New York return for £99; Manchester to Las Vegas return for £199; Liverpool to Morocco return for £44. These are just a few examples of the bargains Sheldon has found for his followers.

What is a mistake fare?

Sheldon, originally from Houston, Texas, says errors that can drop the cost of flights by up to 99 per cent make up around 15 per cent of the deals he sends out. Catching a few himself was part of the inspiration behind committing his life to finding cheap flight tickets.

“The only thing to do to spot a mistake fare is to look everywhere at all times,” he says, adding that laymen travellers might be able to see one on an airline website by pure luck, but he and his team (four other people dotted around Europe) have all sites covered.

“Airline pricing systems are insanely complex,” he says. “Say I’m an airline and I’m setting a fare. That fare then goes into a database and then perhaps into another one that feeds online travel agents (OTAs) and partner airlines, so any single mistake - in a currency conversion or fuel surcharge or airport tax or even a manual error - it goes out into the massive system that is international air fare pricing. And in that lies discounts for travellers.”

Sheldon says he recently spotted mistake fares across all routes offered from the UK by Air Canada: “We told our members and people booked tickets to LA for about £170 or Toronto for £150. And they were honoured by the airline.”

And herein lies one of the issues of mistake fares. If they really are ludicrous (think London-Sydney for £3.50), they will likely be declared invalid by the airline.

“It’s a big PR hit for an airline to cancel a ticket so they have to make a decision on that,” says Sheldon. “But if the mistake only cuts the fare in half, it’s likely they will say it’s valid.”

He estimates that around 60 per cent of all mistake fares, which can swing the other way, trebling the cost of flights, are honoured.

If you do see a mistake fare, it’s best to book direct with the airline, Sheldon says, as a third party agent might add more costs should you want to try to change your flight details later.

What about flash sales?

Beyond the usual sales run by airlines - January often delivers the best offers - carriers sometimes run unannounced - or secret - flash sales that travellers will only find if they stumble upon them.

“Airlines have projections on their routes for how many seats they’ll sell,” says Sheldon. “And if they’re not meeting the capacity they expect at a certain time, they’ll do a little flash sale to get back to normal.”

Sheldon says that analysing fares over time means his Flight Club knows when a sale constitutes a decent saving and when it’s just for publicity.

How do I know when a cheap flight is worth it?

“We try to balance the cost versus convenience,” says Sheldon. “So, for example, a London to Bangkok return with Air China for £300 might sound great, but with a nine-hour layover in Beijing is not a good deal compared to a slightly higher fare with Qatar Airways, a five-star airline, with a short stop in Doha.”

Sheldon says his team often get requests for individual assistance and though they cannot answer everyone’s holiday queries, they try to help when they can.

“We don’t generally help with a specific itinerary but if someone’s in trouble, like their flight has been cancelled or they need to do get home to a sick relative, we try to get them there for less,” he says. “Like a travel agent, but no commission and no bias.”

How to find the cheapest flights

Our consumer expert, Nick Trend, offers more advice on finding cheap flights

1. Know who flies where

Most of your research is likely to be based around fares, but if you want a comprehensive overview of which airlines fly to and from the airports you are interested in, try flightmapping.com.

2. Head to the source

Most price-comparison sites will click you through to an airline’s site in any case, so if you start there, you will at least be sure that you are getting live, up-to-date fares.

3. Or go compare

Price-comparison websites are, in theory, the easiest way to find the cheapest fares. But they can also be misleading. First, most do not list fares from every airline operating the route; second, they do not normally quote exact fares.

This is because they are not quite up to date, because they can’t replicate the many preferences that an individual might have – to check in baggage, for example (see below) – and because they can’t reflect all the different booking fees that might be charged for using different credit or debit cards.

As I found with my spot-check, they can also be subject to technical hitches without the user realising. Even so, they are a useful guide, as long as you bear in mind the limitations and check at least two or three as part of your research.

4. Approach the agents

Sites like Expedia take the booking themselves – you don't click through on to the airline site as you do with the price-comparison sites above.

They can be useful – you can put together packages including hotels and hire cars that are financially protected, for example. But they normally charge a booking fee for flight-only arrangements, and it isn't always clear how much extra you are paying.

5. Fly off-peak

Midweek, outside the school holidays, at unsociable hours etc, and use filters on booking and price-comparison sites that allow you to search for cheaper fares on the days before and after your ideal date.

6. Take hand luggage only

Or book with an airline, such as BA, that doesn't charge extra for hold luggage. Be sure to measure and weigh all luggage – cabin and hold – before you leave home and make sure it is under the limit for your airline. Penalty charges for breaching the limits can be swingeing.

7. Watch for hidden extras

Some sites try to tempt you into booking insurance (which you may already have) and other extras (a new cabin bag, for example). Ryanair is the most aggressive at doing this, and you need to be careful to remove from the online booking form any extras you do not want.

8. Pay by debit card

It is usually cheaper – though you won't have the automatic financial protection against airline failure that you get if you book a fare of £100 or more with a credit card.