Aer Lingus carried just under 1.4 million passengers during August - a monthly record for the airline, and 7.3pc more than in August last year.
The airline - now part of British Airways owner IAG - carried 173,000 passengers on its transatlantic services. That was 16.9pc up on August 2014.
Aer Lingus expanded its services to North America this summer and under IAG ownership is set to add two more transatlantic services next year.
The Dublin-Los Angeles route is likely to restart, while another new service will target the US east coast. Cities including Philadelphia and Miami are likely candidates for a new service.
Aer Lingus carried 965,000 passengers on its short-haul services in August, which was a 5.7pc increase on August 2014.
The load factor on transatlantic routes during August was 93.4pc.