The Centers for Disease Control and Prevention (CDC) has lifted a no-sail order banning cruiseships from US waters alongside a list of Covid-19 safety measures that include sea trials.

The CDC, which is led by Robert Redfield, released the 40-page "Framework for Conditional Sailing" on Friday, while ending an initial 100-day ban that was extended three times to 31 October as the pandemic persisted.

Owners must apply for and attain a "conditional sailing certificate" only after showing effective Covid-19 risk mitigation on simulated sailings with volunteer passengers.

CDC stipulations also include the ability to protect crew from the virus and test passengers onboard.

"These phases are subject to change based on public health considerations and cruiseship operators' demonstrated ability to mitigate Covid-19 risk," the framework said.

The CDC may deny sailing certificates to ships that do not meet its Covid-19 safety requirements, and will suspend sailings for owners whose vessels have infected passengers.

The CDC planned to end the order — imposed in April after a rash of early 2020 onboard virus outbreaks — in mid-February, but it pushed the date forward following intervention from the White House.

The entire cruise sector, which has suffered billions of dollars in losses amid massive fleet lay-ups since March, spoke out against the order in September.

'Step in the right direction'

"[The] Announcement establishes a pathway for our ships to return to service, and that’s an important step in the right direction," Richard Fain-led Royal Caribbean Group said in a statement.

"While we are eager to welcome our guests back on board, we have a lot to do between now and then, and we’re committed to taking the time to do things right."

The New York-listed company said it will train crew members in new health and safety protocols, and hold trial sailings to stress-test measures while at sea.

In September, Royal Caribbean and Frank Del Rio-led Norwegian Cruise Line Holdings formed a Healthy Sail Panel that came up with 74 recommendations for safe sailing that it submitted to the CDC.

The Cruise Lines International Association said it is committed "to implement multiple layers of protocols" designed to mitigate Covid-19 risk and keep crew and passengers safe.

"The economic consequences of the ongoing suspension of service are felt in communities across the United States and with hundreds of thousands of jobs at stake, we are committed to resume sailing in a responsible manner that keeps public health in the forefront," the organisation said.