Boeing Co. stock trading was temporarily halted Tuesday after shares fell by almost 6 percent on reports that regulators plan to keep the company's fleet of troubled 737 Max airplanes grounded until July, far longer than originally planned.

The Federal Aviation Administration released a statement shortly afterward confirming the news, and trading reopened. The planes have been grounded since March after two crashes killed a total of 346 people.

"The agency is following a thorough, deliberate process to verify that all proposed modifications to the Boeing 737 Max meet the highest certification standards," the FAA said. "We have set no time frame for when the work will be completed."

Boeing issued its own statement, saying: "We are informing our customers and suppliers that we are currently estimating that the ungrounding of the 737 Max will begin during mid-2020. Returning the Max safely to service is our number one priority, and we are confident that will happen. We acknowledge and regret the continued difficulties that the grounding of the 737 Max has presented to our customers, our regulators, our suppliers, and the flying public."

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Airline stocks were under additional pressure Tuesday following news that a mysterious new coronavirus had killed six people and spread to Washington state. The Dow Jones Industrial Average tumbled by almost 200 points as travel companies, luxury goods retailers and airlines all took hits as concerns rose that travel would be affected by passengers' fears that they would contract the virus.

Federal health officials confirmed Tuesday that a case of coronavirus had been diagnosed north of Seattle. The patient, a man in his 30s, is in good condition, the Centers for Disease Control and Prevention said. He arrived in the United States around Jan. 15 after having visited Wuhan, China, before airport screenings began.

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Boeing announced last month that it would suspend production of the troubled 737 Max airplanes this month. It still has 4,900 back orders for the jets; its sole competitor, the Airbus A320, is sold out until 2024.

Boeing, which has gone from crisis to crisis in the past 18 months, is in talks to secure $10 billion or more in funding, based on bank appetite, to shore up its finances as costs related to the Max scandal skyrocket.

The company replaced the head of its commercial airplane unit in October and fired Chief Executive Dennis Muilenburg last month, a week after it announced that it planned to suspend production of the Max.

Several hundred embarrassing internal memos have also come to light, each more damaging than the last. In documents Boeing released this month and turned over to Congress as part of an investigation of the jet, one employee says: "Would you put your family on a Max simulator trained aircraft? I wouldn't."

Another message, from April 2017, read, "This airplane is designed by clowns, who in turn are supervised by monkeys."