The man sitting next to me on the plane was not wearing his mask.

Everyone else — every single person I saw — was following the rules. This guy, though, was an American, middle aged, flying back to L.A. from Frankfurt, Germany. His mask was down around his neck.

I ignored him for the first half-hour or so, but finally, nervous about sitting for 12 full hours next to an unmasked man during a pandemic, I asked if he would put it on. I swear I was very polite. Apologetic even.

He ignored me. I asked again, and he finally looked at me and angrily told me that if I wanted him to wear a mask, I would have to get the flight attendant to tell him. He wasn’t going to take orders from me, he said.

So I got up and spoke to the flight attendant, who told him he was required to keep it on — covering both his mouth and nose — for the entire flight. But as soon as she walked away, he pulled it down again, sneered at me, and for the rest of the flight he wore it under his nose.

I said nothing more to him for the remaining 11 hours. I was actually afraid he might become violent if I persisted.

From what I now understand, that may have been a wise decision. Air rage is at an all time high.

According to the Federal Aviation Administration, there have been 4,626 complaints about unruly passengers made so far this year by flight crews. Of those, 3,366 were mask-related. Sarah Nelson, the international president of the Association of Flight Attendants, says that at this rate there will be more incidents in 2021 than in any other year in the history of aviation.

And numbers tell only part of the story. Testimony before a recent hearing of the House Aviation Subcommittee described passengers biting, kicking, punching, throwing trash and food, and screaming racial epithets and slurs. One passenger, angry about the mask requirement, urinated on a lavatory floor; several punched other passengers in the face, according to the FAA. In some cases, passengers followed crew members out through the airport, taunting or threatening them.

Many of the incidents involve both hostility to the mask mandates and excessive alcohol consumption.

It goes without saying that disruptive events that take place thousands of feet in the air carry a special safety risk.

The FAA in January declared a “zero-tolerance policy” for unruly behavior. Among other things, it is no longer offering people warning notices or counseling if they’re found to have behaved inappropriately. The agency is empowered to mete out fines of up to $37,000 per violation. This year it has imposed more than $1 million in fines.

Passengers can also be prosecuted criminally.

Delta Air Lines recently suggested that all airlines should share their “no-fly lists” of unruly passengers. These are people who are banned from flying on one carrier because they’ve behaved badly. In the past, that hasn’t been such a big deal because they can fly instead on other carriers. Sharing the lists could prevent that, although it raises privacy and antitrust issues.

Frankly, I’ve got little sympathy for people who won’t follow the mask rules. They should not be allowed to fly until they can comply.

If I knew my seatmate’s name, I’d wholeheartedly recommend him for a worldwide no-fly ban.

Nicholas Goldberg is an associate editor and Op-Ed columnist for the Los Angeles Times.