Admiral Michael Gilday, chief of naval operations, said Brett Crozier, who was fired as captain of the USS Theodore Roosevelt in April, was guilty of "questionable judgment" in handling an outbreak of COVID-19 aboard the nuclear-powered ship in March.

Gilday likewise faulted Rear Admiral Stuart Baker, Crozier's direct supervisor as the carrier's strike group commander, for poor leadership.

"It is my belief that both Admiral Baker and Captain Crozier fell well short of what we expect of those in command," Gilday said.

"In reviewing both Admiral Baker's and Captain Crozier's actions, they did not do enough, soon enough, to fulfill their primary obligation" to keep the ship's 5,000 crew safe.

After a two-month investigation, the Navy decided that Crozier would not return to the Roosevelt and not be eligible to captain another ship.

Baker's expected promotion meanwhile has been placed on hold, pending further review.

The coronavirus outbreak on board the Roosevelt was one of the first US crises of the pandemic, crippling the massive ship and forcing it to hold for more than a month in port in Guam.

It raised questions about US war-fighting readiness and worries about potential outbreaks on other ships.

More than 1,000 of the crew, including Crozier, ultimately tested positive for the disease, though few showed serious symptoms and only one died.

The case broke into the news after a letter written by Crozier complaining of lack of support in dealing with the outbreak was leaked to the media at the end of March.

While an initial probe seemed to support Crozier's complaints, a deeper investigation showed Crozier and Baker both failed to take good command in the face of the crisis, Gilday said.

They "failed" in evacuating sailors off the ship into sequestered facilities in Guam quickly, he said.

Crozier was focused more on the sailors' comfort, arranging hotel rooms rather than accepting facilities already prepared in gyms, Gilday said.

"Get them off quickly was the primary thing," he said.

"The issue here is really standards of performance particularly in crisis."