Internal flights are under threat after the Government scrapped subsidies for several regional air routes.
Services between Dublin and Derry, Galway, Sligo and Knock will no longer receive public money to help them operate.
Transport Minister Noel Dempsey said improved rail and road services meant they were withdrawing the so-called public service obligation (PSO) contracts on the four routes in July.
The Government is acting on the recommendations of a value-for-money review on the use of state funding for regional airports.
"Having considered the conclusions and recommendations of the review, the Government has agreed to support the continuation of a PSO route between Donegal and Dublin and between Kerry and Dublin," he said.
"In line with the review, the Government has also agreed to cease requiring PSO routes between Dublin and Sligo, Knock, Galway and Derry from July 2011, recognising, inter alia, the improvements in alternative transport modes which have taken place."