The Irish carrier, which is a sister company to British Airways as part of International Airlines Group, has ordered two Airbus A330-300s worth $414 million at list price, although IAG said it has negotiated a “substantial discount” on this price.

Both of these aircraft will be delivered in 2017 and be used to “facilitate expansion on Aer Lingus’ transatlantic network”.

Aer Lingus has developed a strategy of using its Dublin base as a gateway to North America and offers a US customs pre-clearance facility at the airport.

The airline is adding three new US routes from Dublin during the current summer season with a year-round service to Los Angeles, which started in May, followed by the launch of flights to Newark, New Jersey, from September 1 and Hartford, Connecticut, on September 28.

This is the biggest annual increase in Aer Lingus’ capacity to the US since it started transatlantic services in 1958. The expansion will increase daily transatlantic services from Dublin to 28 this summer.

The order for the two new aircraft is the conversion of options on Airbus A330s held by IAG since 2014.