People with coronavirus are still getting on planes. No one knows how many.

In the days after a man on their flight stopped breathing, fellow passengers wondered if he was infected with coronavirus — and whether they might be at risk. The airline said it didn’t know, and the Centers for Disease Control and Prevention wouldn’t say publicly. An answer didn’t come until a local coroner released a report a week later confirming that covid-19 was a cause of the 69-year-old man’s death on Dec. 14, along with acute respiratory failure. By Wednesday, three different passengers said they still hadn’t gotten official word from any public health authorities. The tale of United Flight 591 illustrates the challenges of keeping the novel coronavirus off planes — and informing travelers about possible exposure in a timely manner so they can take their own precautions.