Three flight attendants have filed a lawsuit against Boeing, alleging "toxic" contaminated air made it onto a February 2018 flight and left passengers and flight crew sick.

The lawsuit alleges an incident involving a "dirty little secret": that cabin air on Boeing's commercial aircraft, except for its 787 Dreamliner, could be filled with toxins. That's because they use a "bleed air" system, meaning outside air is brought into the airplane's engines prior to entering the cabin. This air can be mixed with heated jet engine oil, hydraulic fluid and more, including certain chemical compounds that could also be found in insecticides, pesticides and nerve gases like Sarin gas.

USA Today has reached out to Boeing for comment.

The flight in question, Delta Air Lines flight 87, left from Frankfurt, Germany, and was headed to Detroit, according to the lawsuit. The captain diverted the Boeing 767-300 aircraft after people started getting sick, landing in Iqualuit, Canada.

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Emergency personnel evaluated and treated people, and the flight eventually started making its way to Detroit again, only to have flight attendants still show symptoms of illness. Plaintiff Cynthia Milton was removed from the plane during the stop in Canada.

The contaminated air has left the three flight attendants with short- and long-term health effects like nausea, balance problems, tremors, memory loss, vertigo and shortness of breath, among other maladies, according to the lawsuit. They've also lost wages and wage-earning capacity.

iSTOCK The lawsuit claims Boeing "downplayed, minimised and misrepresented the true incidence rate for contaminated air events" (file photo).

"The adverse health effects of contaminated air events are well-documented and serious," the lawsuit states. "The FAA's Office of Aerospace Medicine expert, George Day, describes contaminated air events as when 'a potentially toxic environment is created by contaminated bleed air' and the FAA recognises that exposure to contaminated air events can 'result in a spectrum of adverse health effects.' "

Zoe Littlepage, one of the plaintiffs' attorneys, tells USA Today that this lawsuit came out of research for a separate contaminated air case and ultimately revealed a systemic problem. She says Boeing has had decades of notice and hasn't taken steps to fix it, despite flight attendants citing concerns at industry meetings for more than 30 years.

"It's the asbestos of the skies," Littlepage says.

"Boeing has failed to investigate, study, identify or quantify the toxins present during a contaminated air event: As a threshold step to appropriately addressing the safety hazard of contaminated air events, Boeing knew it needed a comprehensive list of possible contaminants present during a cabin air event," the lawsuit also says. "To date, Boeing still has not finalised a list of such contaminants or surrogates of interest."

The lawsuit also claims Boeing "downplayed, minimised and misrepresented the true incidence rate for contaminated air events," "failed to develop, install or implement filters or converters" and "failed to design, install or implement sensors."

Littlepage says they are asking Boeing to put on a filter in the bleed air system (i.e. air conditioning system) and to put an alarm or a sensor in the bleed air system that could alert pilots if anything got through that filter. The plaintiffs are also seeking US$50,000.

This lawsuit, of course, comes as the company faces intense scrutiny regarding the safety of its Boeing 737 Max plane, which hasn't flown since last year (and major airlines won't be doing so anytime soon).

- USA Today