Aer Lingus carried 2.75 million passengers between Irish airports and Heathrow last year and it is estimated that slightly more than 900,000 of them were connecting to or from other flights.
Heathrow is seen as critical to the Republic’s links to the outside world and the fate of Aer Lingus’s slots there will be at the centre of any debate should International Consolidated Airlines’ Group (IAG) bid to buy the Irish carrier.
The London airport is bursting at the seams. It operates at 98 per cent capacity and will have no more room to grow for at least a decade, even if it gets to provide the British capital’s new runway.
Last year, Dubai overtook it to become the world's biggest international hub. The Gulf gateway plans to grow from 60 million passengers a year to 90 million, an expansion that Heathrow can't match. Emirates flies to Dubai from Dublin twice a-day and offers connections to regions in Asia and the Pacific rim that the Republic sees as potential future markets.
Similarly, Turkish Airlines' service to Istanbul and Etihad's flights to Abu Dhabi also connect to the eastern and southern hemispheres. The numbers flying between middle east destinations and Dublin grew 20 per cent in 2014 to 643,000. A further increase is likely this year as Turkish expands its service.
The latest addition to the stable is Ethiopian Airlines, which will fly from Dublin to Addis Ababa and LA in June. It offers transfers to 49 cities in Africa, where increasing numbers of Irish-based companies, including multi-nationals, are doing business.
Dublin will have 163 flights a week to North America this summer. More than 2.1 million people flew from the capital on these routes last year, and that is set to grow again in 2015. Shannon's transatlantic traffic was up 10 per cent in 2014.
Heathrow is a big player. Based on the three State airports' figures and data from industry publication, Anna Aero, about 3.2 million of those who travelled through Cork, Dublin and Shannon were going to or coming from there. It provided international connections for about a third of them.
However, it cannot get any bigger, while most other routes offer room for expansion. Minister for Transport, Tourism and Sport, Paschal Donohoe alluded to this in the Dáil this week. Given that the airport's strategic importance to us could easily diminish, is it still absolutely necessary to protect all of Aer Lingus's slots there, irrespective of who owns the airline?