Aer Lingus planes at Dublin airport, Ireland. While other European airports are struggling, Dublin is booming.

Dublin - While European airports are looking gloomy because of softening passenger numbers, one airport is bucking the trend.

Olivier Jankovec, director-general for the airports’ body, ACI Europe, spelled out his aviation outlook over the next few years, and for most, it doesn't look good. He blamed: “A continued softening of passenger traffic on the back of lower consumer confidence, fuelled by terrorism and the decision of the UK to leave the EU, as well as major full-service airlines reining in capacity.”

But Dublin’s airport is looking positive.

It has leapfrogged Stansted and Manchester in passenger numbers, to become third behind Heathrow and Gatwick in the geographic area of the British Isles. And it is on course to overtake Copenhagen and Zurich, a remarkable achievement considering they have traditionally been two of Europe’s key hubs.

Like many other airports in the UK and Ireland, it has just reported its busiest-yet July. But what’s particularly interesting is its strongest growth area: transfer passengers. In the first seven months of this year, an average of 2 700 people a day changed planes in Dublin.

That number is small compared with the five top European hubs - Heathrow, Paris, Istanbul, Frankfurt and Amsterdam - but it is up one fifth on 2015. And with the expansion of transatlantic flights from the Irish capital, it looks certain to continue to rise.

This month Aer Lingus starts flying from its hub to two interesting new US locations: Newark, which many business travellers prefer over JFK as a gateway to Manhattan, and Hartford.

To save you looking it up, Hartford is the Connecticut state capital, planted handily halfway between Boston and New York City. While only the fourth-largest city in a small state, it’s an important financial services centre, the “insurance capital of the world”, at least according to locals.

The new link will also provide much easier access to New Haven, home of Yale University, and western Massachusetts.

Dublin’s big selling point for the outbound European market is that travellers can pre-clear US immigration and customs at the Irish airport. On arrival in America, they are regarded as domestic passengers - dodging what can be dreadful queues that typically build through the afternoon with every new touchdown.

Icelandair, another island nation flag-carrier which is building an impressive hub-and-spoke operation across the North Atlantic, does not offer that benefit.

In addition, South African passport holders heading to the US via Dublin do not need visas - either in transit or if they wish to break their journey and see Ireland.

With five times as many passengers as Belfast International, nine times more than Belfast City and 80 times more than City of Derry, Dublin airport is now dominant on the island of Ireland. And success for a hub airport is all about scale: the more flights it has, the more that airlines are inclined to expand services.

One more step is needed to transform Dublin into a formidable transatlantic hub: for Aer Lingus to link up with Ryanair’s European network to offer through-ticketing and guaranteed connections across the Atlantic.