Presidential candidate Bernie Sanders has slammed plans for a Cork-Boston air link saying the carrier, Norwegian Air International, will use non-union labor and destroy good jobs.

In a surprising intervention Sanders stated it would “mark a dangerous precedent” if the route was allowed. US unions claim the carrier would use low paid crew and use Ireland as a flag of convenience.

"Granting such a permit would be a direct violation of the strong labor provisions included in the US/EU Open Skies agreement," Sanders claimed. "Moreover, it would set a dangerous precedent that threatens the jobs of hundreds of thousands of flight attendants, mechanics, pilots, and other airline workers in our country and in Europe."

He added: "We must do everything we can to prevent a global race to the bottom in the airline industry. If this permit is approved, it would open the door to the same 'flag of convenience' model that decimated US shipping."

Cork Airport launching flights to Boston with Norwegian Air. A Cork to New York route may be in store for 2017.

Cork Airport launching flights to Boston with Norwegian Air. A Cork to New York route may be in store for 2017.

Norwegian Airlines International (NAI) has denied the charges. A spokesman for the airline stated: "Some US politicians and unions are continuing to do everything they can to block the competition, preventing passengers' access to affordable airfares, and blocking the creation of new jobs and significant benefits to Ireland and the US."

Read more: US lawmakers opposed to Norwegian Air, including flights from Cork to Boston

"The fact remains that NAI is a recognized EU airline, with a Dublin headquarters, more than 35 aircraft registered in Ireland and a series of new routes from Ireland planned," the spokesman added.

"It is also a clear fact that Norwegian always follows labor laws in all the markets we operate, offering competitive wages and conditions. NAI does not have a single Asian-based crew member or pilot."

Cork Airport managing director Niall McCarthy said the city has "so much to gain" from the planned transatlantic flights.

"We urgently seek the public's help and support to ensure the permit is approved and that the flights are secured once and for all," he said.

Ryanair has also supported NAI. CEO Michael O’Leary said, "NAI will deliver a fresh competitive dynamic on the transatlantic routes by offering choice, service improvements and lower fares to US and European consumers, creating jobs and delivering increased passenger volumes.

A decision on the flights is expected by May 16.