The holiday plans of thousands of ferry passengers have been thrown into doubt due to engineering problems on Brittany Ferries' flagship vessel.
The company announced that the Pont-Aven ferry, which has been out of service since the middle of his month, will now be out of action until June 14.
The cruise ferry sails from Cork to Roscoff in France.
However, it will not sail this weekend and next weekend - just as the busy summer season gets under way.
It is the second summer in a row that holidaymakers taking ferries to France have faced disruption.
Last year Irish Ferries cancelled some 5,700 bookings between Ireland and France after the arrival of its WB Yeats ferry was held up by several months.
The vessel had been commissioned from a German shipyard but was hit by delays.
The National Transport Authority has ordered that Irish Ferries pay compensation to affected customers. However, the company is challenging this in the High Court arguing the situation was not of its making and it was unable to secure another ferry to operate the planned sailings.
Brittany Ferries has announced work to repair the fault on the Pont-Aven, which was taken out of service on May 17, was taking longer than expected.
"It has now become apparent that this work will take longer than initially planned, whilst replacement parts are delivered and installed, and comprehensive checks are carried out," the company said.
The Pont-Aven will not resume sailings until Friday, June 14.
For passengers, that means sailings on the Cork/Roscoff route have been cancelled for this weekend and next, along with a number of sailings to the United Kingdom on the company's Plymouth/Santander and Plymouth/Roscoff routes.
A total of some 6,500 customers will be affected by the cancellations.
Brittany Ferries said it will offer alternative sailings to passengers where available.
Passengers will be given a full refund if the alternative dates are not suitable.
It said it is contacting customers in date order and prioritising those with the "most imminent departures".
Additional sailings will be operated on the Plymouth/Roscoff route, and some Cork/Santander rotations will be diverted to Cork/Roscoff, it said.
"An alternative sailing will be offered where it is available, but if no suitable alternative is available then a full refund will be offered," it added.
Customers have been advised to wait to be contacted by the ferry operator.
However, many passengers have taken to social media to complain about not being able to reach customer service agents.
"We recognise that many customers have struggled to get through on busy lines and that we haven't been able to respond as quickly as we would have liked to concerns via email and on social media," the company told the Irish Independent.
"For this we apologise and we thank everyone for their patience and understanding."
"On behalf of everyone at Brittany Ferries I would like to apologise profusely for the further delays to the return of our flagship 'Pont-Aven', and the disruption that this will cause to travel plans," said the company's chief executive Christophe Mathieu.
The company's technical teams have been working "round the clock" with the Damen shipyard in Brest in France to carry out repairs to the ship's starboard-side steering gear, said the company.
Brittany Ferries' Cork to Roscoff route is a popular summer holiday service that last year celebrated its 40th anniversary.
In 2018, the company also added a Cork to Santander route Ireland's only direct ferry link with Spain.