Flights in and out of Dublin may be delayed from today because of a refusal by air traffic controllers to work overtime.
The trade union Impact says that some controllers are now refusing to work overtime because of the issue understaffing at the Irish Aviation Authority (IAA).
There is no official dispute or industrial action, but staffing levels are so low that the action by individual controllers could affect flights to and from airport, according to a union spokesman.
The IAA was reported last night to have said it was "business as usual" at Dublin airport as far as it was concerned.
However, a spokesperson acknowledged that if there was understaffing in the coming days it might be necessary to impose restrictions on air traffic in the interest of safety.
Air traffic controllers claim that a shortage of controllers has led to a system that is dependent on overtime.
Impact says recruitment has been slow for some time.