“Clearing my throat sounds like thunder,” Ms. Courter wrote in an email from the bus.

All passengers were given N95 respirators — a heavy-duty mask fitted to the face that filters out 95 percent of smaller air particles — to wear on board the repurposed cargo planes, Ms. Courter said.

Some sections of her flight were segregated from others, with those who had tested positive but were not yet showing symptoms sitting in a tented area of the plane, she wrote from on board.

Passengers on the charters were told there would be no overhead luggage space, so all carry-ons had to fit under the seats in front of them, and shipped luggage could not exceed 70 pounds. The converted 747 cargo plane could be cold, the officials said, so passengers were advised to shower and dress warmly. They were also told to take their own food.

Rachel Torres, 24, who had been on her honeymoon with her husband, Tyler, also 24, said they were trying to clean their stateroom so as not to leave a mess for their cabin steward.

“We didn’t sleep much last night,” said Ms. Torres. In preparation for flying, she said, the two were “drinking as much water as we can to hydrate for the flight since we will be wearing masks on the plane.”

Including the cases aboard the Diamond Princess, Japan has recorded the highest number of infections from the new coronavirus outside mainland China. Worldwide, more than 70,500 people have been infected, and at least 1,770 have died, almost all in mainland China.