The Irish Aviation Authority has rejected union claims that the air traffic control system at Dublin Airport is understaffed.
Liam Kavanagh, IAA Director of Human Resources, said the system was not dependent on overtime.
However Michael Landers of IMPACT said there was a serious staff shortage at Dublin's air traffic control.
The Aviation Authority met union representatives today to try to resolve the air traffic controllers' dispute.
The Authority said that air traffic control services operated normally this morning with a full complement of staff.
There had been fears that passengers could face disruption because of an unofficial overtime ban imposed by air traffic controllers from last night because of what they say is chronic understaffing - particularly at Dublin Airport.
The Dublin Airport Authority said it was impossible to predict when and how the overtime ban might affect services, but a spokesperson advised passengers to contact their airline if they were concerned.
Staffing issues
Speaking on RTÉ Radio's Morning Ireland, IMPACT Assistant General Secretary Michael Landers said that a lack of controllers at Dublin Airport and other airports outside the capital was at the heart of the dispute.
He warned that 'traffic levels have now reached the stage where there simply aren't enough controllers to cope on a day to day basis.'
'The service is relying on people working on their days off and on their rest days on overtime to keep the service going. People are just getting tired of that and they've said enough is enough.'
There are more than 300 air traffic controllers in Ireland and 100 of those are based in Dublin.
IMPACT, which represents air traffic controllers, says there has been long standing staffing issues due to inadequate recruitment since the 11 September attacks in the US. It claims it will be at least 2009 before additional staff will have completed their training.
Union sources also stress that overtime is a voluntary matter and that IMPACT has issued no official instructions to implement an overtime ban.
Earlier, the IAA 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.
The IAA also said that it regarded a withdrawal of flexibility as a breach of Towards 2016.
