Capacity at Dublin Airport is to increase from next summer.
The Commission for Aviation Regulation (CAR) has published plans for more departures during peak morning hours.
This will also see a number of changes to runway movements throughout the day.
It will see an increase in the hourly limit on the number of passengers departing both terminals.
The number of departing passengers in Terminals 1 and 2 will increase from 3,375 and 3,450 to 3,700 in each.
There will also be an increased hourly limit on the number of arriving passengers in Terminal 1 from 3,390 to 3,550.
The commission says six parties responded to the proposals.
Aer Lingus opposes the increases, while five others - Cathay Pacific, Dublin Airport, Fedex, Icelandic Air and Lufthansa - supported the decision.
It believes the proposed increases will lead to delays, which will impact Aer Lingus disproportionately, and damage the reputation of Dublin Airport as a connecting hub.
In a statement, the carrier says: "Dublin Airport is already congested and the airfield, taxiway and stand capacity is inadequate to meet current traffic levels.
"Significant improvements need to be made to the existing infrastructure before any increase in capacity during the peak hours should be declared.
"The CAR has itself acknowledged that an increase in the parameters determining capacity at Dublin will lead to an increase in airport related-delays which are already at an unacceptable level.
"These operational delays will have a disproportionate impact on Aer Lingus, which has increasing numbers of guests connecting at Dublin.
"This will also damage Dublin Airport’s reputation as a connecting hub for travel between Europe and North America."