Limited P&O Ferries sailings have restarted between Scotland and Northern Ireland with passenger services due to resume later this week.
Passenger carryings are due to restart on Thursday between Cairnryan and Larne but it remains unclear when key Dover-Calais ferries will return to service.
The company plans to restart sailings from Dover by Easter but this would be “subject to regulatory sign-off”.
Three vessels are moored in Dover and a fourth in a dry dock at the port.
Whitehall sources told the Telegraph that its ferries could remain out of service until May after failing to pass safety checks.
Maritime and Coastguard Agency (MCA) inspections usually take two days to compete but one vessel was detained after failing safety checks more than ten days ago.
The RMT union has warned that it will stage protests at ports when sailings resume in action against the ferry firm sacking almost 800 seafarers last month and replacing them with cheaper agency workers.
The company said it was still experiencing disruption – with Dover-Calais sailings still cancelled – and is providing updates via its Twitter account.