CalMac are urging customers to make any ferry reservations or changes to booking in the next 24 hours, as the online reservations service will be unavailable for a day from 6pm tomorrow (Tuesday 9th October).
The system shutdown is due to a planned period of essential maintenance.
Up until 6pm on Wednesday customers will not be able to make or amend a reservation through the contact centre or in ports.
Online reservations will also be unavailable, although tickets for immediate travel can still be bought at port offices during that time.
With stormy weather forecast for Friday, customers may wish to make changes to their schedule, and should do so either before 6pm on Tuesday or after 6pm on Wednesday.
A statement on the company’s website said: “The upgrade is necessary to improve the reliability and robustness of our servers. Thank you for your patience and understanding during this period.”