Under-pressure CalMac has been searching in vain for six years for extra ferries to bolster its stretched fleet, MSPs were told today.
Managing director Robbie Drummond also "sincerely apologised" for the weeks of disruption caused by a shortage of vessels, which he said had left the firm in an "uncomfortable situation".
CalMac has been forced to cut sailings and deploy smaller ferries on some west coast routes because of prolonged repairs to the MV Clansman, as it has no spare ships.
Mr Drummond said it had been the company's worst disruption for eight years, with the Clansman out of action for more than two months.
He told the Scottish Parliament's rural economy and connectivity committee: "I would like to sincerely apologise to all of our customers for the inconvenience that's been caused.
"We care deeply about our communities and we do understand the economic impact on island residents and businesses, and we are very sorry for the recent disruption.
"Communications have not always been as quick and accurate as we would have liked.
"It's not an easy place for us to be at.
"It's an uncomfortable situation we do not want to be in.
"We have no relief vessel available to provide cover."
Mr Drummond said CalMac and its vessels owner Caledonian Maritime Assets Limited (Cmal) have been looking for additional ferries for six years, and "in depth" for the last two to three years.
"It is clear those vessels are not available.
"To date there have been no vessels suitable."
"We've committed to Transport Scotland, along with Cmal, to continue looking for vessels.
"But as none has emerged in six years that are suitable, there isn't a high expectation that any will emerge in the next six years.
Mr Drummond said ferries had to be suitable for the "challenging" Scottish waters including their shallow depths, and also fit harbours.
He said: "The most likely and obvious way to bring resilience in is to build more vessels for the future."
Two new ferries are being built at Ferguson Marine in Port Glasgow, but their completion has been delayed from the summer to this winter.
Mr Drummond said the fleet was ageing while CalMac's ticket and reservation system was also "life expired and needs to be replaced".
Its problems have been compounded by a boom in traffic triggered by fares being cut under the Scottish Government's road equivalent tariff (RET) scheme
Traffic had increased by 37 per cent over the last five years which Mr Drummond said "had put our services under real stretch".
David McGibbon, chairman of CalMac owner David MacBrayne said: "We are the victims of the success of RET - a huge success across the network."