Four flight attendants are suing Boeing, the world's biggest plane manufacturer, accusing the company of knowing about a defect that allows toxic fumes to leak through the engines and into the cabin — fumes that can cause serious illness.
NBC News' Tom Costello examined this lawsuit, and a coroner's report suggesting a British pilot may have died from toxic fume exposure, in an investigation into the air quality in passenger planes — air all of us potentially breathe when we're on board an aircraft.
For years, flight attendants in the U.S. and Europe have complained about dangerous fumes in the cabin.
On July 12, 2013, Alaska Airlines Flight 769 made an emergency landing in Chicago with four flight attendants seriously ill after complaining of noxious chemical fumes in the cabin. Two of the flight attendants passed out, including Vanessa Woods.
"The next thing I knew was on the galley floor, and the other flight attendant was on the PA system just mumbling incoherently," Woods told NBC News.
Paramedics rushed all four — who were sick, disoriented and struggling to concentrate — to the hospital. Two years later, three of them, including Woods, say tremors, neurological and memory problems still prevent them from returning to work.
Now, all four are suing Boeing, accusing the plane manufacturer of exposing them and the plane's passengers to toxic fumes that seep into the plane's ventilation system.
"I got on that flight, I was healthy and I got off the flight and I have never been the same since, Woods said.
Most modern aircraft are ventilated by bleeding outside air through the plane's engines and into the cabin, but experts say if a seal inside the engine leaks, burning oil can mix with the cabin air. The flight attendants' attorneys sat that happens once a day, somewhere in the world.
The lawsuit suggests Boeing has been aware of the danger for decades, citing internal documents including a 2007 email from a Boeing engineer who laments: "Bottom line is I think we are looking for a tombstone before anyone with any horsepower is going to take interest."
"We know that Boeing has known this problem exists since the early 1950s," flight attendants' attorney Rainey Booth told NBC. "They've known there's a problem, they know there's fume events, they know the contaminants come in through the bleed air."
Emergency landings for fumes or smoky cabins are not unusual, but there's no good data on how many passengers might have suffered ill effects.
In 2012, British Airways pilot Richard Westgate died. He'd been on medical leave for 15 months, after claiming he'd been poisoned by toxic cabin fumes. In April, a British coroner found "symptoms consistent with exposure to organo-phosphate compounds in the aircraft cabin air."
Here in the U.S., the FAA tells NBC News: "We are concerned that if certain mechanical failures occur, the cabin environment may contain contaminants."
The nation's largest flight attendant union estimates hundreds, perhaps thousands of crew members and passengers have been exposed over the years, but may not realize it.
"They may not realize that they're sick or that it was caused from this contaminated air," Sara Nelson of the Association of Flight Attendants told NBC. "So they are not getting properly treated for that poisonous fumes that are now in their system."
Boeing has been sued before and settled. The manufacturer is declining to comment on this suit, but has studied the issue in the past and found: "Cabin air is safe to breathe. Research has consistently shown that cabin air meets health and safety standards and that contaminant levels are generally low."
Boeing also says it's looking for ways to improve its planes and cabin air is one of many subjects it's studying. The flight attendants' suit calls on Boeing to stop using the bleed air system in new planes, and to put air quality sensors in planes already flying to warn pilots if toxic fumes are leaking into the cabin.
Notably, Boeing's newest plane — the 787 — does not use the engine bleed system to ventilate the cabin.