Gillian Brockell is a video editor at The Washington Post.

It happened during the boarding process on a flight from Fort Lauderdale to JFK in the fall of 2009. I had long earlier learned that the key to a pleasant flight was to greet everyone as they walked onto the plane, so I stood in the front galley and said my hellos.

Suddenly, a middle-aged white woman leaned uncomfortably close to me and whispered, “There is a man, four people behind me, in a green shirt, who is very suspicious.”

I whispered back: “Okay. What’s he doing?”

“You’ll see,” she said, wide-eyed.

I thought two things: This woman is probably racist. And I need to take her seriously.

As a former flight attendant for a major carrier, I wasn’t surprised to hear that a Southwest Airlines passenger reported University of California student Khairuldeen Makhzoomi as suspicious after he said “Inshallah” (“God willing”) during a phone call conducted in Arabic while boarding a flight at Los Angeles International Airport this month. Flight attendants are often made to play referee when hundreds of humans with wildly different life experiences are crammed into an aircraft cabin.

It’s usually simple stuff, like asking a young woman who has never seen a Hasidic Jew if she can switch seats with her boyfriend so she’s not touching the devout man next to her. (She, of course, has the right to say no.) Or moving the man with the severe dog allergy as far away as possible from the blind woman’s service animal. Or asking the bachelor party to pipe down for the umpteenth time, because not everyone is going to Las Vegas to get drunk.

But sometimes you’re asked to be someone’s accomplice — in their racism, their homophobia, their cruel joke about the larger person seated next to them or their demand that the mother in front of them drug her children to shut them up. For professionals who are supposed to be polite, it can get awkward. The expression “Takes all kinds!” becomes your best friend.

This past week, Southwest released a statement saying that the passenger who reported Makhzoomi also spoke Arabic and was alarmed by the content of his conversation, not the language itself. Makhzoomi says he was telling his uncle in Baghdad about attending a speech by U.N. Secretary General Ban Ki-Moon and made a passing reference to the Islamic State. The airport police agency says Makhzoomi made no threats and broke no laws. It is not illegal to mention the existence of the Islamic State on an aircraft.

But to me, the most shocking thing about the whole story is that, according to Makhzoomi, from the time the other passenger reported him to the time he was asked to leave the plane, he had no interaction with the flight attendants.

Flight attendants are trained extensively in evaluating suspicious behavior with videos, checklists, regular exams and drills. (And drills and drills and drills.) This infuses you with an automatic, paranoid vigilance that follows you forever and insists that you take all threats seriously, since the cost of being wrong is too high.

But nowhere did our training recommend that we accept a passenger’s assessment of a situation, and nowhere did it teach that speaking Arabic is cause for suspicion. It’s unlikely that any airlines do. I contacted all of the major U.S. airlines this past week to ask about training procedures. United Airlines, Frontier Airlines and Southwest declined to reveal any details. A spokesman for American Airlines said the company never trains crew members to perceive the Arabic language, Arab- or Muslim-style clothing or a Middle Eastern background as suspicious.

During that 2009 flight, after the woman alerted me to the “suspicious” passenger, I thanked her and told her I’d check it out. I watched the man closely as he stepped onto the plane, looking for signs of a terrorist. Was he jittery? Nope. Was he sweating? A little bit, but we were in South Florida; I was sweating, too. Was he wearing unseasonable clothing, like a big coat in the summertime? No. In fact, his Green Bay Packers jersey perfectly fit the season — football season. Did he have trouble following a normal conversation?

“Hi, how’re you doing today?” I asked.

“Fine,” he said, nodding casually.

“Going home?” I asked.

“Nope, wedding,” he said.

All right, no problems there.

A few minutes later, after he reached his seat, I walked down the aisle to assess the situation again, the woman who flagged him tracking me with her eyes.

Did he hold on tightly to a piece of luggage? No, his roll-aboard was in the overhead bin. Did he sit stiffly? Nope, he was slouched in his seat, headphones on, already watching the game on the seat-back TV. Not exactly the actions of a person who believes he’s about to die.

In fact, the only thing he appeared to have in common with the 9/11 hijackers was that he was brown. He could have been Punjabi or Puerto Rican; I have no idea. He could have been a Catholic, or a Sikh, or one of the many hundreds of millions of Muslims who have nothing to do with terrorism. I let it go and had no further discussion with the man or the woman, other than to serve them drinks and bid them well when they disembarked.

I hope, and I think it’s likely, that the man never noticed what was happening. In other cases, airlines have ended up on the losing ends of lawsuits. In 2006, Iraqi immigrant Raed Jarrar wasforced to change his T-shirt, which said “We will not be silent” in English and Arabic, before boarding a JetBlue Airways flight. JetBlue and the Transportation Security Administration eventually paid him $240,000 to settle a lawsuit. In another 2006 incident, six imams were removed from a US Airways flight after they prayed in the departure lounge at Minneapolis-St. Paul International Airport; the airline and the imams eventually settled out of court.

Southwest, despite this incident, has a long-standing reputation for friendly customer service. I know Southwest flight attendants, and even in the relative privacy of their Facebook feeds, they talk about genuinely loving their passengers and the work they do to keep them safe and comfortable. But that comfort must include filtering out passengers’ biases and flight attendants’ own.

Heather Poole, a flight attendant and the author of “Cruising Attitude,” puts it this way: “Flight attendants don’t live in a bubble. We don’t get to pick and choose who we associate with. We rub elbows with the world. . . . Has a passenger ever made me nervous? Yes. Did we kick that passenger off? No. I just kept on eye on them. Did anything happen during the flight? No.”

I grew up in a wealthy, mostly white, mostly Mormon town out West. Respecting God’s will was a frequent topic of conversation among my friends. And, like lots of future pilots and flight attendants, my favorite toy was the globe. I’d spin and spin it, dreaming of all the different, “exotic” places I’d go. Becoming a flight attendant made my dreams come true. That included travel to Muslim-majority countries, where the frequent incantation of “God willing” was far from exotic — it reminded me of home.

When passengers report an issue, it’s impossible to know what their life experiences are. That’s why it’s so important to make assessments based on training. In this case, being polite and being vigilant should have called for the same thing: a conversation. Anyone who makes a snap judgment from the cocoon of the galley has no business being a flight attendant.