Third-quarter revenue was negative $33.7 million, a rare event for an S&P 500 company, as it reversed previously recorded income from refunds and cancellations. Analysts were expecting revenue of $12.4 million.

"It's been almost 7 months since we paused our cruise operations, and every single day has been extremely frustrating and challenging on so many levels," Chief Executive Officer Richard Fain told analysts.

The cruise industry has come to a virtual standstill after many vessels became hotbeds of infection and some operators even faced lawsuits for onboard outbreaks.

To resume operation and stem the losses, the company and its peer Norwegian Cruise Line have submitted their recommendations, detailing health protocols, to the U.S. Centers for Disease Control and Prevention.

Royal Carribean said it was planning to start a series of trial sailings with just the crew to rehearse the COVID-19 protocols before bringing in consumers on one or two of its ships on short voyages.

Prices for cruises in the second half of 2021 are down slightly even as bookings remain within historical ranges, the company said, echoing larger rival Carnival Corp's comments.

Royal Carribean posted a net attributable loss of $1.35 billion in the third quarter and also warned of another loss in its current quarter.

Excluding items, it lost $5.62 per share, bigger than analysts' average estimate of $5.12, according to Refinitiv data.

Shares of the cruise operator, which have lost 60% of their value, were down marginally.

(Reporting by Praveen Paramasivam in Bengaluru; Editing by Patrick Graham and Arun Koyyur)