The world’s most popular plane trips

Plane Talk: Of the top 100 air routes, the cheapest is between Izmir and Istanbul, with plenty of seats at under £13

Air bridge: a pedestrian bridge on Jeju Island, Korea, one end of the world's busiest air route (Simon Calder)

A secondary airport of an Asian capital, and an island that is not exactly up there with Bali or Barbados as a dream travel destination: that does not sound a particularly promising air link. Yet it turns out that this is the world’s busiest air route by a country mile.

The two ends of the perennially chart-topping link are Seoul’s Gimpo Airport (which was eclipsed when the much bigger, smarter Incheon opened in 2001) and Jeju Island, which for many Koreans constitutes the most accessible holiday getaway.

Accordingly, last year there was one departure between the two every eight minutes on average, carrying 200 passengers.

The trip details are very similar to London-Dublin: 280 miles, 70 minutes “block time”. Most links of this length would be operated by narrow-bodied Airbus or Boeing jets. But I flew between the two on an Airbus A330. From Korean Air's perspective it was a worthwhile misuse of a long-haul, wide-bodied aircraft to meet the demand for lift, and to profit from the preparedness of passengers to pay an average of £72 each way.

If you like your island to be volcanic with beaches, rather like the Canary Islands, Jeju is a very pleasant place to be. And it is as far south as Crete. Well worth checking out if you happen to be in Seoul; book well in advance and travel off peak, and you will find there are plenty of seats around the £25 mark.

The headline figures revealed by Routesonline, for its World Routes 2018 gathering in Guangzhou this weekend, come as no great surprise. Second place, a long way behind the 13.4 million passengers on Gimpo-Jeju, is the link between Australia’s two biggest hubs, Sydney and Melbourne. Nine million passengers a year show how desperately needed a high-speed rail link is between the two cities.

But the Australian intervention is the sole non-Asian route in the top 10. Domestic routes in Japan, India, Indonesia, China and Vietnam fill most of the rest of the places, with Hong Kong-Taipei the only international link (6.7 million passengers a year).

Looking at the top 100, the average route length was 722 miles (the same as Birmingham-Barcelona) and the mean fare was £130.

The UK makes an appearance for being one end of both the longest and the most expensive route in the top 100: London Heathrow to New York JFK, where the average one-way fare is £490. I imagine that is skewed by a lot of high-value business travel.

But the LHR-JFK link, with 8,145 passengers a day on average, has now been supplanted as the busiest international route starting or ending in Europe by Heathrow to Dubai – which has 8,795 a day.

New York JFK is also one end of the busiest route in North America: the transcontinental link to Los Angeles International.

And for the cheapest? Head for Turkey. The link between Izmir in Turkey and Istanbul’s second airport, Sabiha Gokcen, has an average fare of only £42 for 200 miles of air travel (the same as London to Amsterdam or Paris).

With Turkish Airlines, there are plenty of 98 lira fares available – currently just under £13, which happens to be the same as Air Passenger Duty in the UK. It’s a great time to be an air traveller, but not to be an airline.

Researchers used OAG Schedules Analyser to calculate the top 500 routes by seat capacity, then used data provided by Sabre Market Intelligence to figure out how many of the passengers were occupied