For Ms. Choma, those remaining flights provided a financial cushion. After the pandemic halted the photography business she has nurtured on the side, she took on flights from colleagues who couldn’t, or wouldn’t, staff them.

Some airline employees have continued to show up reluctantly, either because they need the money or fear losing their jobs once the crisis has ebbed. Others who had once relied on extra income from loaded-up schedules now have to make do with what few flights are available. Tens of thousands more have taken unpaid leave, staying home out of necessity or concern or to free up slots for colleagues who may need the income more.

Already, hundreds of flight attendants and pilots have fallen ill and at least five have died from the coronavirus, according to the labor unions that represent them. And even though the industry secured $25 billion from the federal government to pay employees through September, the future remains bleak.

Many airlines are likely to emerge from the crisis with fewer employees, and a full recovery isn’t expected any time soon. It took several years for passenger volume to rebound after the terrorist attacks in 2001, a shock less severe than the current crisis, which is seen by many as the worst in the history of aviation.

The devastation arrived abruptly in late February as new bookings started to plummet and cancellations began to surge. Less than two months later, air travel has fallen to new lows. On Tuesday, for the first time since the Transportation Security Administration was formed after the Sept. 11 attacks, the agency screened fewer than 100,000 travelers, pilots, flight attendants and airport and airline workers at its checkpoints. On the same day last year, it screened more than two million people.