Some ferry services operated by P&O have resumed between Scotland and Northern Ireland after a vessel servicing the Larne-Cairnryan route was released from detention.
The European Causeway was detained at the port in Larne last month due to safety concerns after the company sacked almost 800 workers.
The Maritime and Coastguard Agency (MCA) released the ferry on Friday following a reinspection, which took place at the request of P&O.
The ferry company said on Monday that some services had now resumed sailing on the route amid confusion for passengers.
It posted on Twitter than it had resumed a three-services-per-day schedule for passengers and freight.
The DP World-owned company operated freight-only sailings on Sunday.
P&O has been prevented from running all but one of its vessels since it announced widespread redundancies on March 17.
The company sparked outrage by replacing its crews with cheaper agency workers without giving staff any notice.
Criminal and civil investigations have been launched into P&O Ferries’ move.
A spokesperson for the MCA said last week: “The European Causeway has been released from detention following a reinspection of the ferry over the past two days.”
P&O Ferries chief executive, Peter Hebblethwaite, told a joint hearing of the Commons’ business and transport committees last month that his company broke the law by not consulting with trade unions before sacking workers.