Ryan Knudson (3:22)

Here's something I can't say I've ever really thought much about. When you're on an airplane, where does the air you breathe come from?

Benjamin Katz (3:29)

The answer, the air that we breathe in an aircraft, with one exception, in terms of modern day aircraft, comes via the engine.

Ryan Knudson (3:38)

When a plane's at altitude, the air outside is too thin for us to breathe. It needs to be compressed. So decades ago, engineers devised a solution. They'd redirect some of the air that was already being compressed in the airplane's engines and send it to us in the cabin. This system is called bleed air. Today, it's used on pretty much every commercial aircraft. The one big exception is Boeing 787. But sometimes this bleed air system goes wrong. The seals that are supposed to keep engine oils out of the air supply degrade fuels leak. And that's when you get a fume event.

Benjamin Katz (4:18)

A fume event is when oils and other engine or hydraulic fluids leak into that compression chamber. The temperatures inside the engine reach during takeoff, you know, in excess of 600 degrees Fahrenheit. And so any leak of oil into that section of the engine immediately vaporizes and then mixes into the air that gets fed to us in the cabin and to our pilots in the cockpit.

Ryan Knudson (4:46)

What happened on that Delta flight you heard about earlier was an extreme case. So much oil leaked and vaporized into the air so quickly that it created clouds of white smoke. More typically, though, there's no smoke at all, just a smell.

Benjamin Katz (5:04)

They call it the dirty sock smell. It smells like dirty socks.

Ryan Knudson (5:07)

How dirty? Like after a workout or like just after a long day or maybe just wearing slippers around the house.

Benjamin Katz (5:14)

It's incredibly unscientific, which is part of the problem.

Ryan Knudson (5:16)

I mean, you know, some people do like to take off their shoes on.

Benjamin Katz (5:20)

Airplanes, and they have smelly feet completely. The difference here is that it permeates throughout the cabin. And something that, you know, I think is really important to, to just say is the majority of not just vapors in an aircraft, but smells are not related to toxic oil.

Ryan Knudson (5:39)

Fume events have been a problem ever since the invention of the bleed air system. For decades, though, the smell of cigarettes helped cover it up. But when smoking on airplanes was banned, it got more noticeable. So what's been the airline industry's sort of conventional wisdom about these fume events?

Benjamin Katz (5:58)

The industry acknowledges that oil can leak into the bleed air system, right? That is established and agreed. The industry also recognizes that there are toxic chemicals that are included in the oils that leak and Vaporize in the bleed air. What they say, though, is that the contamination levels of these toxic chemicals into the air supply is too low to cause any kind of real damage or concern or injury.

Ryan Knudson (6:27)

The industry also says that these fume events are rare.

Benjamin Katz (6:30)

As a reference, the FAA on its website states that fume events occur fewer than 33 times per million departures.

Ryan Knudson (6:41)

But Ben started to get curious after an industry source suggested he look into fume events. That offhand tip eventually led Ben and a team of reporters to conduct over 100 interviews and review FAA and NASA reports, internal industry documents, and research papers. The question they started with was, how often do fume events actually happen?

Benjamin Katz (7:06)

And to try and verify what the FAA refers to as rare, we looked at a database that the FAA keeps. It's called the service Difficulty Report database.

Ryan Knudson (7:16)

When something goes wrong in flight, airlines are required to submit a report to the service difficulty report database. And there are all kinds of issues in there, from reports of burnt muffins in the first class oven to engine malfunctions to fume events. Fume events aren't systematically tracked in this database, but they are described. For instance, a report might say that the crew noticed a dirty sock smell or that oil was leaking from an engine. Ben and his team pulled reports going back 15 years, over a million reports total. And they used AI to comb through them, looking for instances of fume events. What did you find?

Benjamin Katz (8:00)

So we found a massive increase. You know, if we look back to 2014, we identified a rate of 12 fume events per million departures. But by 2024, that number had increased to 108. So this really massive and consistent spike that started in 2016 and 2017.

Ryan Knudson (8:22)

So almost a tenfold increase, according to your data?

Benjamin Katz (8:25)

Basically, yeah.

Ryan Knudson (8:27)

While the Journal's analysis put the number of fume events today at about 100 per million flights, Ben and his colleagues came across one industry analysis to put the number higher. According to an internal document from a member airline, the International Air Transport Association, a trade group found there were more than 800 fume events per million departures in the U.S. ben and his colleagues took their findings to the Federal Aviation Administration. In a statement, the agency attributed the increase in fume events in part to a change in its guidance for reporting these events. Though that change only took effect last November, the agency said that the increase in fume reports reflects a healthy safety culture that values critical safety reporting. Was this big spike in fume event reports surprising to you?

Benjamin Katz (9:17)

Yes, surprising because we knew that not much technically had changed to these aircraft Right. Again, to reiterate this point, bleed air systems have been deployed on aircraft for decades. Right. So what led to the change in 2017 that triggered this massive spike?

Ryan Knudson (9:37)

And were you able to find an answer to that question?

Benjamin Katz (9:41)

Yeah, we did.

Ryan Knudson (9:45)

Ben and his team discovered that while almost every commercial aircraft flying today experiences fume events, one aircraft in particular was.

Benjamin Katz (9:52)

Driving the spike, the Airbus A320, which.

Ryan Knudson (9:57)

Just so happens to be the best selling family of planes in the world. Why that plane? What was going on?

Benjamin Katz (10:06)

After a bit of digging, what we discovered is Airbus had just released their brand new version, an upgraded version of the A320 called the Airbus A320neo. And it had an engine that had serious issues and very publicly acknowledged issues with those seals in the compression chamber that was allowing oil to leak into the air supply. And so when Airbus started delivering these planes, the airlines got very frustrated. And in 2016, early 2017, airlines started to really complain to Airbus about fume events.

Ryan Knudson (10:42)

Airlines were frustrated because a fume event isn't just a smelly annoyance, they can be costly. That's because after a fume event, according to official Airbus manuals, the airplane had to undergo maintenance, leaks had to be investigated, and the plane decontaminated. As a result, planes were being grounded for up to days at a time, causing canceled flights, lost revenue, and angry passengers. How did Airbus respond to these complaints from airlines?

Benjamin Katz (11:14)

They said that they agreed with the airlines. They described fume events in their maintenance documents as, you know, posing a minor discomfort to passengers. Just really kind of framing it as it's a bit of an inconvenience. Passengers don't love it, crews don't love it because it smells a bit bad. In which case we don't think that you need to, under certain conditions, do this really heavy maintenance that we've been asking you to do for decades. Right. And so Airbus changed the manuals.

Ryan Knudson (11:43)

The updated manuals, for example, said that if the smell wasn't that bad and hadn't occurred in the previous 10 days, the airplane could keep flying. So Airbus response to these complaints wasn't to change the airplanes, it was to change how the airlines needed to respond.

Benjamin Katz (12:02)

Exactly. And that's when the data really showed the spike in increase.

Ryan Knudson (12:09)

In the data. Ben and his team saw the same airplanes recording fume events time and time again. One plane recorded six fume events in one month. Airbus, Boeing and the FAA declined interview requests from Ben and his colleagues. An Airbus spokesman said the company's planes are designed and manufactured according to all applicable rules and requirements. In a statement, the company added that it's committed to, quote, continuously enhancing our products, working closely with operators and regulators to ensure the best possible cabin environment for passengers and crew. A Boeing spokesperson said the cabin air inside the company's planes is safe and, quote, no indoor environment is free from contaminants. The data were clear. According to Ben and his team's analysis, fume events were on the rise. And that was concerning because Ben and his team were also starting to doubt the industry's other key claim about fema, that they aren't a significant threat to health. That's next.

Benjamin Katz (13:23)

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Ryan Knudson (13:27)

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Ryan Knudson (14:30)

Early in his reporting, Ben connected with a former flight attendant named Florence Chessen.

Benjamin Katz (14:36)

Her story was really quite incredible. She had been working for about 17 years as a flight attendant for JetBlue. It was a second career for her. She's incredibly bubbly, like, loved the job. Just absolutely loved the job. She was on a flight to Puerto Rico from Boston. As they started to prepare for landing, they started to notice a smell. She had kind of come out the bathroom. Her colleague asked her, you know, do you smell that? Florence kind of looked at her and then inhaled. She describes it as kind of inhaling in a single deep breath, you know, like. And she said that she instantly felt like she'd been drugged. She said that she, she felt like she was a pair of floating eyeballs, you know, walking down the aisle trying to figure out what was going on. The aircraft, you know, landed safely and then passengers kind of refolded for the, for the return flight back to Boston. And on this return flight, that's when things kind of, you know, really escalated.

Ryan Knudson (15:38)

Chessen described feeling a metallic taste in her mouth she was sweating profusely, both common symptoms of toxic exposure. Two of her colleagues were also affected.

Benjamin Katz (15:49)

One of them was struggling to breathe, so she was given oxygen. And another one was not just struggling to breathe, but actually started vomiting on the aircraft.

Ryan Knudson (15:59)

Chessen's flight landed back in Boston, and her two colleagues were immediately taken to the hospital, one of them in a stretcher. But for Chessen, the nightmare wasn't over the first year.

Benjamin Katz (16:13)

I can probably, on her behalf, describe as kind of the most difficult of her life, you know, waking up in the morning with, you know, she described it as if her brain had been lit on fire, that somebody had opened it up, poured in gasoline, and then just lit a match.

Ryan Knudson (16:29)

Her husband noticed a chemical smell radiating off her for weeks. Some symptoms still haven't gone away. To this day, Chesson says she still suffers hypersensitivity to sound, light, and everyday chemical smells.

Benjamin Katz (16:42)

So, you know, a task like going to the supermarket where they've just cleaned the floors with a cleaning solvent, you know, is not. Is not something that you can feasibly do anymore.

Ryan Knudson (16:52)

Chessen saw several neurologists about her condition. Scans of her brain revealed a symmetrical pattern to the damage.

Benjamin Katz (17:00)

If you can imagine it, the air runs through up your nostrils, immediately passes through your blood brain barrier, and very symmetrically does damage all the way through from the front to the back of your brain. So the symmetrical nature of the injury is what's led a lot of the neurologists that have treated her to determine that, you know, the fume event and the. And the inhalation of contaminated air is what caused her injury.

Ryan Knudson (17:28)

Dr. Robert Konecki, one of the doctors who examined her, compared the damage to her brain to a concussion an NFL linebacker might experience after a brutal hit. And he should know. He's a consultant for the Pittsburgh Steelers. Chessen hasn't worked since.

Benjamin Katz (17:44)

That flight was the last flight she ever took.

Ryan Knudson (17:47)

A spokesperson for JetBlue emphasized that the airline takes customer and crew member safety seriously. While cabin air quality concerns are not isolated to JetBlue, we continue our work to identify policies and procedures to reduce and manage them, unquote. It's not just flight attendants who are at risk. Ben and his team spoke with doctors who collectively have treated hundreds of flight attendants, pilots, and a few passengers, many with similar stories and symptoms. Should we be concerned that this is also happening to the people who are operating the airplane?

Benjamin Katz (18:26)

It's not only an additional safety risk, it's an additional safety risk that the industry acknowledges.

Ryan Knudson (18:33)

In 2015, the United nations published a paper identifying Fume events as a risk to flight safety.

Benjamin Katz (18:39)

And we reviewed a number of incidents where the pilots have described their vision narrowing or losing feeling in their fingers or in their arms, or just feeling drugged in the way that Chasten described feeling drugged. There was one pilot who described flying and when he landed, describing it as if, you know, he felt like he was dreaming.

Ryan Knudson (19:01)

One thing I've been wondering is, if the air is contaminated and it's being pumped through the airplane, wouldn't it impact everybody on board equally?

Benjamin Katz (19:10)

It's a really great question and really pivotal. It's really two things. The first thing is that our DNA is obviously all very different, and depending on your DNA, that affects your susceptibility to different toxins. That's very well established. The second thing that's really important is that, you know, from some of the doctors we've spoken to, there's kind of pretty clear evidence that repeat exposure is important here, that your susceptibility increases kind of the more times that you've been exposed.

Ryan Knudson (19:41)

How did airline companies respond when you brought this reporting to them?

Benjamin Katz (19:45)

I mean, the comments were, you know, flying is. Is. Is one of the safest forms of travel in the world. And cabin air quality is, generally speaking, very, very high. We got kind of a lot of that confidence that they meet the regulatory standards, you know, their aircraft are certified, that fume events are rare, and that there are no long term health conditions associated with it.

Ryan Knudson (20:09)

How could this be fixed and how big of a deal would it be to fix it?

Benjamin Katz (20:14)

There are some immediate things. The first, most obvious thing is do the proper maintenance and make sure that the aircraft is decontaminated after an incident. Right. That feels like the most basic thing to be done. Install monitors so we can actually find out exactly what's in the air. Not just that, but it would allow pilots to immediately identify when a fume event is happening. Right. Instead of relying on crew literally smelling it through their noses, there are filters that can be developed and installed. So, yeah, there's a lot that can be done.

Ryan Knudson (20:44)

But so why hasn't it? I mean, if we're decades into this, why are we still having this problem?

Benjamin Katz (20:50)

There are a lot of solutions, but it requires the industry to recognize that there's an actual problem to be solved. One thing to know about aviation safety is it's a cost risk analysis. With any issue that compromises safety in aviation, the faa, other regulators around the world, they always look at what is the chance of this happening, what is the risk to passengers or crew, and what would it cost to actually fix the problem. You know, there is very much this kind of cost factor.

Ryan Knudson (21:26)

Airbus is taking some steps to reduce fume events. Last year it told airlines about some upcoming changes it said would reduce what it calls smell in cabin events. The most significant of these changes involves moving an air inlet from the belly of the jet to the top. But that change won't be rolled out until next year and it'll only be applied to new aircraft, not to planes already in service. I feel like this information is going to change the way I feel about flying.

Benjamin Katz (21:59)

Yeah, Yeah. I think if you and I were sitting in a pub and you asked me like, would I fly tomorrow? Like, yes, I personally would fly tomorrow. I think, you know, even at the industries higher level of incident rate, you're still talking 800 incidents per million departures. The odds of it happening on your flight are still very low. Right. The problem is that the odds of it happening today somewhere in the US is almost guaranteed.

Ryan Knudson (22:42)

That's all for today. Tuesday, September 23rd. The Journal is a co production of Spotify and the Wall Street Journal. Additional reporting in this episode by Andrew Tangle and John West. Thanks for listening. See you tomorrow.