Dublin Airport — Dublin, Ireland

Dublin Airport, listed under the code DUB, ranks as Ireland's dominant aviation gateway and serves as the primary base for both Aer Lingus and low-cost giant Ryanair, two carriers whose combined route networks blanket Europe and stretch across the Atlantic to North America. A US Customs and Border Protection preclearance facility, one of just a few outside America, lets travelers clear immigration before departure so arriving flights land as domestic services once they touch down stateside. The airport's two runways, including a newer north runway completed in the early 2020s after decades of planning disputes with nearby residents, support one of the busiest schedules in Europe for an airport of Dublin's size. Positioned north of the city center along the coast, DUB has grown enormously alongside Ireland's economic transformation since the 1990s.