Interislander's operator is promising to cough up for ferry disruptions.

A Commerce Commission investigation found KiwiRail may have breached the law by suggesting cancelled sailings were out of their control.

Mechanical events leading to cancellations will now almost always trigger compensation.

Chief customer officer Adele Wilson says people incurred some high costs from cancellations. 

"As we were trying to catch up the schedule, we had another event - and so people who'd been rebooked, unfortunately some of them were delayed again."

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