Now, the coronavirus threatens to put all of that to the test.
The latest example of the outbreak’s toll on the industry came  Wednesday, when United Airlines became the first U.S. carrier to  announce a widespread cut to domestic service, signaling that fear over  the virus was starting to erode ticket sales far from the hot spots of  the epidemic.
In a letter to employees, the airline’s top two leaders announced  plans to cut international service in April by about 20% and domestic  service by about 10%, with similar cuts possible in May. They also  announced a hiring freeze through June and said workers in the United  States could apply for voluntary unpaid leave.
“We sincerely hope that these latest measures are enough, but the  dynamic nature of this outbreak requires us to be nimble and flexible  moving forward,” Oscar Munoz, United’s chief executive, and J. Scott  Kirby, who will take over that job in May, said in the letter.
Trans-Pacific flights, for which demand had fallen starkly as the  virus seized Asia, will be halved in April, while trans-Atlantic service  will be cut by about 10%. Latin American service will be reduced by 5%.
In a statement in response to the United announcement, Sara Nelson,  president of the Association of Flight Attendants, said the airline was  taking “a responsible approach” in responding to the coronavirus  outbreak.
Business leaders and the administration are seeking to allay concerns about the virus and its toll on the industry.
Thomas Donohue, chief executive of the U.S. Chamber of Commerce, said  at a news conference Wednesday that the airline industry didn’t need  “bailouts,” though he said that if regional airlines encountered  difficulties, “we’ll figure out a way to bring assets together to keep  them flying.”
“Bottom line is we’re going to run just like business as usual, with a little higher heartbeat, and get it done,” he said.
Later, at a White House meeting with airline executives, President  Donald Trump dismissed a reporter’s question about whether the federal  government would provide financial assistance to the industry. “Don’t  ask that question, please,” he joked. “Because they haven’t asked it. So  I don’t want you to give them any ideas.”
Trump and Vice President Mike Pence, who also attended the meeting,  sought to allay public fear over the outbreak. “It’s safe to fly,” Trump  said. “And large portions of the world are very safe to fly. So we  don’t want to say anything other than that.”
As the virus has spread, the administration has been in close contact  with representatives of the travel and tourism industry, according to  Scott Solombrino, executive director of the Global Business Travel  Association, an industry group for corporate travel managers. Officials  at various agencies addressed concerns and provided updates to industry  officials on a Monday call, for example.
At the same time, the Centers for Disease Control and Prevention is  seeking the authority to compel airlines to share data on passengers and  crews arriving from abroad who may be at risk of exposure to the  communicable disease. The airline industry has argued that such a  requirement would be too onerous and instead recommended that the data  be assembled from various agencies that collect passenger information.
After the financial crisis, the aviation industry underwent a period  of consolidation, during which airlines focused on increasing capacity  and efficiency. In recent years, they squeezed profits from new, premium  offerings and by harnessing a shift, driven by millennials, toward  valuing experiences more highly than goods.
As a result, airlines ended 2019 on a positive note, but reports of  the coronavirus outbreak began surfacing at the start of January. Before  the month was out, it had spread far enough that all three airlines had  announced plans to suspend service to China, the center of the  epidemic, because of plummeting demand.
Since then, shares of United and American Airlines have lost about a  third of their value. Delta is down somewhat less, about 18%.
United said last week that the effect of the coronavirus on its  first-quarter earnings would be offset by lower fuel costs. But it  withdrew its financial guidance for the rest of the year.
JetBlue also separately said on Wednesday that it would reduce  service temporarily by about 5% and would take several steps to shore up  cash, including reducing hiring, offering voluntary leave and limiting  spending.
Since January, airlines have reduced or canceled service to Hong  Kong, South Korea, Japan, Italy and other destinations, as demand for  travel abroad slid. And while international routes make up only a small  share of major airlines’ service, they are significantly more profitable  than flights within the United States.
But there are growing signs that domestic  demand is starting to suffer, too, as concern spreads among the public,  corporate events are canceled, and large businesses ask employees to  refrain from flying.
On Tuesday, Ford Motor Co., which employs nearly 200,000 people, told  workers to stop all international and U.S. domestic air travel and to  use videoconferences as much as possible for critical meetings.
General Motors, which employs about 164,000 people, has stopped all  worker travel to China, Japan, South Korea and Italy, and restricted  international travel to other locations only for essential matters.
How long such bans will last is unclear, according to a poll  conducted last week by the Global Business Travel Association. Among  corporate travel managers who had canceled or suspended employee trips,  only 31% expected to lift such restrictions within three months. More  than half, 54%, said they didn’t know when the travel would resume.
To address similar uncertainty among the broader public, United,  Delta and American have all said in recent days that they would waive  change fees for flights booked in the coming weeks.