CITYJET, the Air France-owned airline, has joined Ryanair in calling for separate passenger charges at the two terminals in Dublin Airport.
CityJet said it was in favour of so-called 'differential pricing' when the new passenger terminal, T2, opens in November.
The airline is set to remain in the existing terminal and will be its second-biggest user after Ryanair.
The Dublin Airport Authority sought a hike in passenger charges to recover the cost of building the new terminal. But it wants the increases applied to users of both facilities.
Cityjet and Ryanair said this was unfair as they would not be using the terminal. The Commission for Aviation Regulation had ruled that the DAA could increase its passenger fees by 40% next year to €10.44 per person if the second terminal opened on schedule.
An Aviation Appeals Panel ruling earlier this month found that the regulator must revisit the proposed increase and consider differential pricing.
CityJet said in a submission to the regulator that its position was that users of "T2 should bear the full costs of its use".
Aer Lingus on Friday agreed to move all its operations to T2 but said it would review that decision in the event that differential pricing is introduced at Dublin Airport.
Terminal 2 has cost the DAA about €600m and has been built to handle 15 million passengers a year. Passenger numbers through the existing terminal fell 13% in 2009 to 20.5 million, the first decline in nearly 20 years.