Princess Cruises announced on Friday that it’s extending its pause in operations again, impacting all of its cruises scheduled through March 31, 2021, and cruises longer than seven days sailing in and out of U.S. ports through Nov. 1, 2021. It’s also canceling cruises in and out of Japan through June 25, 2021.

The Carnival Corp.-owned cruise line said the extended pause was necessary to meet preparations required under the conditional sailing order rules set by the Centers for Disease Control and Prevention (CDC.) The CDC’s framework requires cruise ship operators to plan for testing, quarantining, social distancing and other health precautions amid the ongoing outbreak of COVID-19.

“We are focused on preparing our ships to meet the CDC health and safety requirements for our eventual return to service,” Jan Swartz, president of Princess Cruises, said in a statement.

Guests whose trips have been canceled will be able to request a full refund using Princess’ online form by Dec. 31. Otherwise, they will receive a refundable future cruise credit equal to the fare paid, plus a 25% nonrefundable bonus future cruise credit.

Princess isn’t the only cruise line to cancel trips into next year. Carnival Cruise Line announced this week that it was canceling all U.S. cruises through the end of January, plus cruises embarking from some cities into February and March. Royal Caribbean Group has also suspended its sailings through the end of 2020.

Passengers are apparently eager to return to the seas, even as the pandemic escalates. On Sunday, Royal Caribbean CEO Michael Bayley said that 100,000 people have volunteered as passengers for the company’s trial cruises that are required for the CDC’s conditional sail order.

“We can’t wait to start this next phase with you all,” he wrote in a Facebook post.

While cruise lines pause their operations, they will likely be holding some simulated voyages to meet the CDC requirements. The mock trips will include everything a normal cruise does – from check-in to dining and private shore excursions – but cruise lines haven’t yet said how they’ll pick volunteers or even whether general members of the public will be eligible.

A SeaDream Yacht Club vessel, the first ship to resume sailing in the Caribbean, recently had to cut its trip short and cancel upcoming voyages when several passengers tested positive for COVID-19.