When to book cheap flights and how to get the best deal

David Holcroft is a man with a late-summer mission. “We want to book return flights from Manchester to Athens, going out on 31 August, returning 9 September. Prices are quite high at the moment.”

He realises I am not a travel agent (heaven forbid), but he has an important principle he wants to check: “I have been told to wait 12 weeks before the flight date to get the cheapest rate.

“Is this true advice, or just poppycock?”

David has wisely decided to travel to travel to the Greek capital in September. The city is a joy as the summer heat starts to subside, along with air fares. Usually.

But before I address David’s precise problem, a reminder of how fares are calibrated. The model for airline pricing is that, in a perfect world, fares start relatively low and gradually increase. The airline would like to reach a price climax in the last few days before departure. The few remaining seats should be sold at for sky-high fares, on the basis that anyone booking in the final days is really keen to travel and therefore price-insensitive.

So a Manchester-Athens flight for 31 August 2019 might go on sale in October 2018 at £40, then increase at around £10 per month – making it currently £110 one-way – until the last week of August, when it leaps from £140 to £300, or whatever the airline thinks it can get away with.

That is the theory. But as any airline revenue manager will tell you, what they would like to happen and what actually occurs in practice are often two completely different things.

While peak departures generally just get relentlessly more expensive, off-peak flights are much trickier. Airlines have a firm sales trend, which simplistically might involve selling 10 per cent every month before departure. If tickets are selling “above trend” – ie, too fast – the fare goes up; all too often, though, the fares are below trend and the fare goes down. But the closer to departure, the twitchier the airlines become. As you know, once a plane departs with an empty seat, that is potential revenue which has gone forever.

I’ve not heard the “12 weeks” line before. I daresay fares for some flights reach a minimum at that point before departure. But in my experience, airlines start to fret about particular flights around two months before departure and will, if necessary, keep fares low right up until a few days ahead of take-off.

The only Manchester-Athens flight on 31 August, easyJet’s afternoon departure, is currently priced at £118 one way. That looks as though it is on trend and may well nudge up. But what about the Wizz Air flight from Luton departing at almost the same time for £63? Agreed, it is a three-hour bus or car journey from Manchester, but you might consider that worthwhile.

Looking at return flights on 9 September, there is clearly something driving demand from Athens to the UK. I’m surprised that demand is strong enough for Wizz Air to command £107, with easyJet to Manchester nearly twice as much.

In your position, I wouldn’t be a buyer of the easyJet flight at over £300 return. I might commit to the Wizz Air trip, but more likely I would wait until a month beforehand. And I would also be looking for flights from other locations in Greece. For example, easyJet has a flight from Thessaloniki to Manchester for £94. The newly upgraded rail link means Greece’s second city is only four hours from the capital – and a worthwhile location in its own right if you can arrange to spend some time there.

Finally, for destinations in Australia, I find that 12 hours, never mind 12 weeks, is quite sufficient. Checking this morning from Manchester to Sydney tonight there is plenty of choice this afternoon and evening on top-quality carriers Cathay Pacific and Emirates for around £800 return. While you may find yourself sitting next to someone who paid less, it’s more likely they will have paid a lot more. For ultra-long flights, patience is a virtue in more ways than one.