Irish carrier Aer Lingus will begin flying to Philadelphia next year. The airline revealed the new Dublin-Philadelphia route as it rolled out its updated schedule for summer of 2018.

Flights will begin March 25, when Aer Lingus begins flying four weekly flights between the cities. Aer Lingus will use 177-seat Boeing 757 narrowbody jets for the service. 

The launch of the Philadelphia route furthers a robust trans-Atlantic expansion for Aer Lingus since it's acquisition in 2015 by International Airlines Group (IAG), the parent company of British Airways and Iberia. Since then, Aer Lingus has begun service to four other U.S. cities: Hartford, Conn.; Los Angeles; Miami and Newark. Combined with destinations it had already served, Aer Lingus will be flying to 11 U.S. airports once the Philadelphia flights start. 

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"We are delighted to announce Philadelphia as our new route for summer 2018,” Aer Lingus chief operating officer Mike Rutter says in a statement. “We are proud to continue to deliver on our promise to grow our transatlantic network and further strengthen Dublin Airport as a leading gateway from North America.”

Aer Lingus' new route will put it into head-to-head competition with American Airlines, which operates one if its busiest hubs in Philadelphia. American flies non-stop to Dublin with Airbus A330 widebody jets. 

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American is close partners with IAG’s British Airways, but it does not have a similar relationship with Aer Lingus. (Related: Aer Lingus could enter oneworld in 2017, says IAG CEO | Aer Lingus CEO on U.S. growth plans, oneworld frequent-flier alliance)

IAG CEO Willie Walsh has previously said the company plans to move Aer Lingus into the oneworld frequent-flier group that also counts American, British Airways and Iberia among its member carriers. Speaking to Today in the Sky in late 2016, Walsh said the timing was uncertain. He suggested then that such a move could come as soon as this year, though no subsequent news has been announced with 2018 now less than three months away. 

"IT (information technology) tends to be the issue that drives the timeline on most of this -- getting the Aer Lingus systems capable of interacting with the other oneworld carrier systems," Walsh said. 

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Oneworld or not, Aer Lingus indicated its U.S. expansion plans are far from done. The company noted that it’s set to begin receiving more aircraft that can be deployed on trans-Atlantic routes. Among those: a new long-range version of Airbus’ popular A321 narrowbody that will be able to fly further than previous versions. 

“The future holds bright and interesting prospects for Aer Lingus as eight new Airbus A321 Long Range aircraft are set to join our fleet in the coming years and by the end of this year, 2017, we will welcome another brand new Airbus A330,” Rutter says in Aer Lingus' statement about Philadelphia and the carrier's trans-Atlantic plans.