Carnival Cruise Line hopes to operate up to four cruise ships this summer if the industry can get approval from the U.S. Centers for Disease Control & Prevention.

Carnival said its plan is to operate Carnival Vista and Carnival Breeze from Galveston and Carnival Horizon from Miami. Further, if a solution is found to allow cruising in Alaska, Carnival Miracle will assume some of Carnival Freedom’s departures from Seattle.

Even if the CDC allows a cruise restart, Alaska operations still face Canada’s ban on cruise ships in its waters through February 2022.

All other Carnival cruises through July 30, 2021, have been canceled .

“We continue to have constructive discussions with the CDC but still have many questions that remain unanswered. We are working diligently to resume sailing in the U.S. and meet the CDC guidelines,” said Christine Duffy, president of Carnival Cruise Line. “We sincerely appreciate the continued patience and understanding of our guests and travel advisor partners and will share additional information as quickly as we can.”

Since there is still some uncertainty about whether the cruises will operate, Carnival said guests booked on those sailings may cancel without penalty by May 31, 2021, and receive a full refund. Guests whose cruises are canceled are eligible for a future cruise credit and onboard credit or a full refund.

Separately, late last week Carnival notified its guests that Carnival Splendor’s pause out of Sydney was extended another month, as it canceled sailings from Aug. 19 to Sept. 17, 2021.