Trade union Unite says it cannot guarantee that full emergency cover will be provided during a strike at Waterford Airport.

Members of the union started an indefinite strike this morning at the airport and around a dozen workers are on the picket line at the gates of the airport.

The union says the strike follows a decision by airport management to cut workers' hours from 39 to 21 per week without agreement and claims the workers have effectively been locked out.

Airport management say they are surprised and disappointed with the industrial action, adding that the airport's revenues fell sharply since VLM Airlines discontinued scheduled passenger services on the Waterford-London Luton route in June.

The withdrawal of the route led to a very significant loss of work available at the airport.

Management says the cut in hours for staff is necessary and that most staff understand and support the airport's decisions.

The airport stresses that it is business as usual for all commercial aircraft, training and leisure activity, visitors and the SAR (Coast Guard helicopter) with all operational functions taking place as usual.

The airport continues to search for a new airline to provide passenger services to/from Waterford.

A union spokesperson said it is unclear if all emergency cover will continue to be provided if the strike continues and possibly escalates.

At present, emergency cover is being provided. Management said there is no threat to emergency cover during the strike as there is enough staff to continue ground/air operations as normal.