A legal bid to stop strike action at the country's main airports in the run-up to St Patrick's Day is due before the High Court.
The Dublin Airport Authority and Ryanair are trying to secure an injunction against SIPTU.
SIPTU is planning a four-hour work stoppage at Dublin, Cork and Shannon airports this Friday.
Strike action is due to take place between 5am and 9am.
It is part of a long-running dispute about cuts to pension benefits at Aer Lingus and the Dublin Airport Authority.
However, the DAA and Ryanair claim the strike is unlawful and they want injunctions stopping the industrial action which coincides with the France v Ireland rugby match and the busy run-up to St Patrick's Day.
Ryanair says if the action does go ahead it would affect 13,500 of its customers.