The fallout from the virus poses Boeing’s greatest challenge since the Sept. 11, 2001, terrorist attacks, when it cut production in half and laid off tens of thousands of people. Company insiders say the pandemic is far worse, since it has touched every continent other than Antarctica and plunged nearly every airline worldwide into crisis.

“It’s not just Boeing,” said Susan Houseman, director of research at the Upjohn Institute for Employment Research. “Its supply chain may be irreparably damaged. There will be bankruptcies, companies will lose their workers, and they just can’t restart in six months.”

Boeing executives are furiously drafting contingency plans and trying to find a way to keep factories open and avoid mass layoffs or furloughs, three people familiar with the deliberations said. Executives from the medical, financial and human resources teams are monitoring developments constantly, and have identified several potential situations that could cause production to grind to a halt, one of the people said.

Boeing executives believe the most likely possibility is that the government effectively mandates a work stoppage, either by shutting down all nonessential businesses or instituting strict travel restrictions, such as border closures or shelter-in-place orders.

Factories could also shut down if too many employees at one facility become sick, raising the risk of community spread on the factory floor. And supply-chain disruptions could become so severe that Boeing does not have the parts it needs to make planes.

Boeing is bracing for a rise in absent workers, either because school closings force parents to stay home or because people are too scared to leave the house. Already, some workers have begun to stay home, one of the people briefed on the plans said.

Should plants have to shut down, Boeing could move them into a state of “suspended operations.” Under such conditions, some Boeing employees might still be paid. And if workers at the company’s factories in Washington State are sick, they may be eligible for the state’s paid family and medical leave.