Delta, American and United announced they will temporarily cancel all of their mainland China flights in response to the coronavirus outbreak, facing pressure from unions representing airline employees and new warnings from public health officials.

As of Friday, the outbreak had infected nearly 10,000 people, most of them in China, and killed more than 200, all in China.

The U.S. State Department late Thursday elevated its China travel advisory to level 4, recommending that Americans do not travel there. That change followed the World Health Organization's declaration of a global health emergency over coronavirus.

White House officials said Tuesday they were considering a China travel ban but said then they had not contacted the airlines. Friday's decision by all three domestic carriers to suspend their service all but rendered White House action moot, though the administration did declare the coronavirus to be a public health emergency in the United States late Friday.

"The risk of infection for Americans remains low," said Alex Azar, secretary of Health and Human Services and chairman of the coronavirus task force set up by President Donald Trump. "We are working to keep the risk low."

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American Airlines

American cited the State Department's updated travel advisory Friday in suspending its U.S.-China routes immediately through March 28. The airline said it would contact the affected customers directly to help them make alternate travel arrangements.

"We will continue to evaluate the schedule for March 28 and beyond and make any adjustments as necessary," the airline said in a statement.

Delta Air Lines

Atlanta-based Delta on Friday said it would suspend its U.S.-China flights from Feb. 6 through April 30.

Delta usually operates 42 flights a week between its U.S. hubs and China. It said Friday that the last China-bound flight would depart the U.S. on Monday, and the last return flight would depart China on Wednesday.

"The airline will continue to monitor the situation closely and may make additional adjustments as the situation continues to evolve," the airline said Friday in a statement.

United Airlines

United said Friday it would suspend operations between its U.S. hub and three mainland China cities – Beijing, Chengdu and Shanghai – from Feb. 6 until March 28. The carrier said it would continue to operate one daily flight from San Francisco to Hong Kong.

"Until that date, we will continue to operate select flights to help ensure our U.S. based employees, as well as customers, have options to return home," the airline said Friday in a statement. "As always, the safety of our customers and employees is our highest priority and we will continue to monitor the situation as it develops."

Pressure from unions

Late Thursday, the union representing 28,000 flight attendants at American Airlines called for the airline and the federal government to ban China flights.

The Association of Professional Flight Attendants' call followed a lawsuit filed Thursday in Dallas by the Allied Pilots Association, which represents 15,000 American pilots, to halt the carrier's flights between the U.S. and China. The flight attendants' union said it supported the pilots' union's court action.

The union's national president, Lori Bassani, praised American's move in a statement, saying union members are pleased to learn the airline had suspended all flights to mainland China.

She also noted that "all of our flight attendants and pilots who were in the air at the time of the halt have returned back to the United States."

American's pilots union Thursday called on its members to decline assignments to fly China, citing the "unacceptable risk."

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Earlier airline flight cuts

Earlier this week, United was the first domestic carrier to adjust its China flights and it further pared back its U.S.-China flight schedules Thursday, extending the cuts through the end of March.

Delta and American announced their initial schedule changes Wednesday, following United's cuts on Tuesday and signals from the White House that it was considering a China flight ban.

All three domestic airlines serving China had already have issued flight waivers for travelers who don't want to travel there, allowing them to postpone or cancel plans without the usual penalty.

Contributing: Dawn Gilbertson, Jayme Deerwester