Ryanair is to seek a High Court injunction against SITPU's plan to stage a four-hour work stoppage at three airports next week.
The airline says it will not allow more than 13,000 of its customers to be "blackmailed" by what it describes as "greedy SIPTU unions".
Ryanair says the attempt to shut down air access in Dublin, Cork and Shannon is "unlawful, unnecessary and unfair to passengers".
The airline said in a statement: "In the event that the strike goes ahead Ryanair will make every effort to minimise the disruption to our customers who will be contacted early next week with details of any rescheduling of their flights.
"Ryanair calls on the Dept of Transport to explain what contingency plans the Government will put in place to prevent Ireland’s vital airports being closed by SIPTU if this legal action is unsuccessful. Is the Government planning to call in the Gardaí and the army to keep airport security and fire services open next Friday? If not, why not?"