The wearing of masks to protect against the coronavirus has become such a sensitive issue in the United States that airlines are struggling to impose the practice on defiant travelers in the enclosed environment of an airplane.
Johannes Eisele, an AFP photographer, experienced the problem in person.
He recently took his seat on an American Airlines flight from LaGuardia Airport in New York City -- then a coronavirus hot spot -- to Charlotte Douglas International Airport in North Carolina. He had a middle seat, wedged between two other passengers -- only one of whom was wearing a mask.
As Eisele recounted it, "I asked him if he didn't have a mask. He said, 'Yes, I have.' And I asked him, 'Can you please wear it?'"
"He said he feels more comfortable without the mask and he won't wear it."
When Eisele told the man that "I feel more comfortable if you wear it," his seatmate replied, "Keep your fear to yourself."
The flight was completely full, so Eisele was unable to change seats.
The scene occurred early this month, shortly before US airlines imposed mask rules -- generally exempting only passengers with medical or religious excuses, or very young children -- to slow the spread of COVID-19.
At the time of boarding, say officials at American Airlines and United Airlines, the rule is clear: no passenger can board a flight unless he or she has a mask on.
The problem occurs after takeoff. Those airlines generally will, if necessary to avoid confrontation, allow people to remove masks while in flight. They are allowed to do so as well, of course, while eating or drinking.
If a passenger's refusal to wear a face covering causes a disturbance, a United spokesman told AFP, "we've counseled our flight attendants to use their de-escalation skills."
He added, "They do have the flexibility to re-seat customers on the aircraft," though that does not work on a sold-out flight.
"Our employees are not expected to control the personal behaviors of customers," said a Southwest spokesman. The airline does provide masks in airports and onboard planes but will not "deny boarding based solely upon a customer not wearing a mask."
- 'Do not escalate' -
An internal advisory from American Airlines to its flight attendants explains how they are expected to handle mask-related problems.
If a passenger declines to wear a mask for reasons other than medical or religious, it says, "please encourage them to comply, but do not escalate further."
Similarly, if a customer is frustrated because a seatmate fails to wear a face covering, "please use situational awareness to de-escalate the situation."
"During the pandemic, we must partly rely on common sense and responsible actions" by travelers, the Southwest spokesman said.
In short, the airlines appear to have chosen the course of conciliation over confrontation with insistent and sometimes angry travelers -- even it means a greater health risk to others sitting nearby.
The wearing of masks has to some extent been politicized by President Donald Trump, who has refused to wear one, in the face of virtually unanimous medical advice and even after some White House staff members have contracted the coronavirus.
Scientists say the risk of infection is near its highest when people spend long periods in enclosed spaces -- like airplanes.
Not to wear a mask on an airplane "is hugely irresponsible," said Jonathan Metzl, a professor of sociology and psychiatry at Vanderbilt University, in Tennessee.
"I think if someone doesn't wear a mask on a plane, they should be arrested."
- Mask as political symbol -
Deciding not to wear a mask in one's own car is one thing, Metzl said, but refusing to do so while in public transport is a different matter.
"I think that President Trump and the Republicans have successfully coded a mask as a political symbol," he added.
"They're basically rallying their base by suggesting that wearing a mask is a sign of submission, or that people who wear masks are weak."
Beth Redbird, a sociology professor at Northwestern University, has been studying Americans' behavior during the pandemic.
"Republicans who are skeptical of Donald Trump support social distancing," including the wearing of masks, she said, while "independents who are supportive of Donald Trump are skeptical of social distancing."
On Thursday, the chairman of the House transportation committee, Peter DeFazio, urged the airlines to "leave at least one seat-width of spacing between passengers."
In a letter to a group representing the major airlines, he said they could "adjust fares as needed" to account for emptier planes.