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The vaguaries of the weather have long been accepted as something beyond the control of even the biggest cruise lines. Even in an age of robot barmen and huge megaliners, you can’t beat mother nature.

And for decades, cruise passengers have accepted that their chosen form of holiday is at the mercy of forces bigger than mankind.

But today, that implicit understand seems to have changed. Two court cases involving Australian lines seem set to put the way passengers are treated in such circumstances on trial.

The latest involves the Carnival Spirit, one of our favourite ships.

According to The Sunday Telegraph, a cyclone forced the vessel to turn back from New Caledonia last March.

Instead of sailing in the sunny Pacific, passengers ended up in Melbourne and Hobart – the very cities they had flown out of a few days earlier to catch the ship.

One mum was quoted as saying: “I thought my kids were going to learn about new cultures. Instead, we went back to Melbourne.”

Carnival Cruise Lines maintains Cyclone Pam was upgraded a few hours out from Sydney, forcing an itinerary change. According to passengers involved in a class action, there were warnings four days before.

Had passengers been advised of the risk, say their lawyers, they would have cancelled and claimed a full refund. Instead, they received $150 on-board credit and a 50% discount on another cruise.

A Carnival Cruise Lines spokesperson said, of course, the safety of passengers was paramount. “When passengers boarded the Carnival Spirit in Sydney, it was our full intention to deliver a South Pacific cruise itinerary.”

Scenic, the luxury Australian river cruise line, has carried many thousand of happy customers around the world in an illustrious career that has seen the line win many awards for service.

Yet it has faced the threat of a class action which could involve hundreds of clients over how it handled the European rains two years ago.

Heavy rain in France and Germany caused massive flooding on the Rhine, Saone, Rhone and Danube rivers in 2013.

Many lines cancelled cruises, allowing clients full refunds. Scenic bussed its clients to many locations and ships leaving some to claim they hadn’t actually received a cruise at all.

The company maintains it was operating within its contract.

Passengers – including a partner in the law firm taking what could turn out to be a landmark action – claim instead of cancelling their cruises, Scenic and associated company Evergreen Tours used coaches to move them around during the floods.

One couple said they spent their life savings – $26,200 – on what they expected to be a river cruise through the French and German countryside. Instead, they spent hours on “substandard coaches, including one without a working toilet and air-conditioning”.

Chief Operating Officer of Scenic Tours, Damien Thomas, released a statement at the time saying: “Unfortunately, we have no control over the weather. These were extreme circumstances with this level of flooding only occurring every 100 years.

“We do, however, always respond as best we can in these challenging circumstances, and aim to provide the highest quality service and travel experience at all times including when a change to an itinerary is necessary due to prevailing weather or river conditions. The quality of the guest experience is always our top priority and we always do our utmost to limit the impact on their holiday.”

In a statement lodged with the court, the company points to the terms and conditions of its contract, including: “We may substitute (at the nearest reasonable standard) another vessel or motor coach for all or part of the Itinerary and also provide alternative accommodation, where necessary…where we make a variation to the itinerary, we are not liable to you for such variations.”

Should these cases proceed to court, it is likely to place under scrutiny clauses that have been in place for many decades. Whether they result in beneficial changes remains to be seen.

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