Carnival Corp continues to hold off sailings for a large chunk of its ships after postponing the return to operations in US and Canada for key brands Carnival Cruise Line, Princess Cruises, Holland America Line and Seabourn Cruises.

Carnival Cruise Line, the Arnold Donald-led cruise major's biggest brand with 23 ships, has extended its suspension of operations from US ports until 1 June. A date for the return to sailing has not yet been determined.

"We continue to work on plans to resume operations and are encouraged by the focus to expedite vaccine production and distribution, which are having a demonstrated impact on improving public health," president Christine Duffy said.

Meanwhile, Holland America, Princess and Seabourn have all pushed back some sailings to and from Alaska and Canada as they review plans due to the Canadian Transport Ministry's interim order that closed Canadian waters to passengerships.

The order will stay in effect to 28 February 2022, but the cruise brands are all trying to salvage itineraries that travel to and from Canada, Alaska, the US West Coast and New England.

"This will include several Alaska, three Canada/New England and two Pacific Coastal cruises in summer and fall of this year," Holland America said.

Holland America, which has 14 ships, has not yet cancelled Alaska cruises departing from mid-May and sailing round-trip from Seattle, Washington.

"Discussions are underway with Canadian and US government authorities to try to find a path forward to preserve these sailings," the brand said.

"However, we must be practical in our approach by acknowledging the limitations put in place by the current Canadian order that requires us to cancel select sailings."

Princess, which has 17 vessels, has also cancelled some of its cruises to and from Alaska and Canada as it also tries to figure out resuming such itineraries once Canada's order passes.

"Princess is engaged with various US and Canadian government officials to try to preserve a portion of the Alaska and Canada and New England 2021 cruise seasons," the brand said.

"In the meantime, Princess has committed to operating the Kenai Princess Wilderness lodge along with McKinley Chalet Resort in Denali and Westmark Fairbanks Hotel this summer."

Seabourn, which has six ships, has cancelled its 2021 departures from Alaska and British Columbia, Canada.

The cancellations apply to 19 voyages scheduled in summer 2021 between Vancouver, Canada and Juneau, Alaska, including one Pacific Coast voyage at the end of the season.