Four flight attendants are suing Boeing, claiming that toxic air from an engine leaked into their plane and made them seriously ill on a 2013 flight.
A lawyer for the four said Tuesday that Boeing has known for decades about the potential danger of drawing warm air off jet engines to heat airplane cabins.
Boeing Co. declined to comment on the lawsuit, which was filed in an Illinois state court in Chicago.
Similar allegations have been raised before. In 2011, Boeing settled a case brought by an American Airlines flight attendant; terms were sealed.
In April, a British coroner reported that samples from a British Airways pilot who died in 2012 were "consistent with exposure" to toxic fumes in cabin air. The airline said research shows that the level of dangerous fumes in planes isn't high enough to pose a health risk.
So-called bleed air is used to heat the cabins on most commercial planes, although Boeing's newest aircraft, the 787 or Dreamliner, uses a different system.
The Federal Aviation Administration says studies have shown cabin air is as good as air in offices and homes, but a spokeswoman said the agency is concerned that contaminants can get in if equipment fails.
Airlines are required to report incidents involving fumes, and FAA says from 1990 to 2010 there were about 900 of those. U.S. airlines operate about 9 million flights a year, according to government figures.
Boeing has repeatedly said that independent, industry and government researchers have found that cabin air meets health and safety standards.
But lawyers for the flight attendants suing Boeing say that company documents suggest Boeing knew of the risk that bleed air could contain dangerous byproducts of burning engine oil.
They said that a Boeing engineer tried but failed to draw management's attention to the issue, concluding in a 2007 email: "Bottom line is I think we are looking for a tombstone before anyone with any horsepower is going to take interest."
The women were working for Alaska Airlines when they say that all four became sick and two passed out during a Boston-to-San Diego flight. The one-year-old Boeing 737 jet made an emergency landing in Chicago, and all four were taken to hospitals, according to the lawsuit.
Even weeks later, "I knew something was seriously wrong with me. I just was not the same person," one of the flight attendants, Vanessa Woods, said on conference call with reporters Tuesday. She said she suffered from fatigue, tremors, memory loss and concentration problems and was unable to return to work.
Lawyers for the women said they weren't aware of any passengers who got sick. They attributed that to the women having been on the plane longer, before passengers began boarding, and that the air might have been more toxic higher in the cabin where standing flight attendants would breathe it.
(David Koenig - Associated Press)