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CHARLOTTE, N.C. -- The US Airways Boeing 767 plane where 15 people got sick Jan. 16 had been taken out of service twice in recent weeks for a foul odor.

Flight 1041 from St. Thomas in the Virgin Islands was met by ambulances when it landed in Charlotte after passengers and crew complained of headaches and nausea they attributed to a suspicious smell. Eight passengers were treated on the scene. Seven crew members were taken to the hospital, where they were treated and released.

Maintenance logs obtained by NewsChannel 36 show the plane -- tail number 0251 -- experienced a similar problem on Dec. 28 and Dec. 30 on flights to San Juan, Puerto Rico. One note in the report reads, WHEN THRUST LEVERS WERE REDUCED TO IDLE FOR INITAL DESENT [sic ]A VERY STRONG ODOR SMELLING LIKE WET SOX [sic] AND/OR DIRTY FEET CIRCULATED THROUGH THE PASS. CABIN AND FLT DECK.

Crew members got sick on board those flights, according to Judith Murawski, a scientist with the Association of Flight Attendants who studies cabin air contamination.

US Airways spokeswoman Michelle Mohr said the plane was grounded and serviced on both occasions. After the second incident, it was taken out of the rotation until Jan. 5, when it was cleared for flight. Mohr said mechanics determined that the problem was a leak of the hydraulic fluid Skydrol.

The plane flew 24 flights without incident in between Jan. 5 and Jan. 16. The Jan. 16 problem has not yet been officially diagnosed, though Mohr notes that a finding of a hydraulic fluid leak is likely. The plane is currently grounded.

Murawski told NewsChannel 36 the problem is far more widespread. Her research indicates there are an average of 0.86 incidents of contamination in the cabin and flight deck per day.

This happens fleet wide, she said.

It is standard industry practice to provide air to the cabin by compressing outside air in the plane's engine, conditioning it, and then circulating it into the body of the plane. (The air inside the cabin is also constantly recirculated.)

Your average passenger has no idea that the air that they're breathing is coming off the engine, Murawski explained. Sometimes the engines leak oil and those oils are highly toxic.

Engine oil contains toxic chemicals including tricresylphosphates (TCPs) and carbon monoxide. Hydraulic fuel, while slightly less serious, also contains toxic chemicals. Leaks involving those substances are often the source of a foul odor that many describe as a dirty sock smell.

It came out of nowhere...lasted for about 5 minutes. Just a strong smell, like smelling in your shoe, described one flight attendant, who experienced cabin air contamination on a flight last year. She spoke to NewsChannel 36 on the condition of anonymity, to protect her job. Passengers noticed it. Flight attendants -- immediately we were alarmed.

That flight attendant says crew members on her flight suffered from headaches, loss of taste and flu-like symptoms. Some are still experiencing health problems.

She believes passengers may never know what happened. Flight attendants went off that plane sick, and most likely passengers did as well, but they have no idea, she said.

If they smell a dirty sock smell they think the person before them has taken off their shoes, Murawski said. It doesn t occur to them that they are being exposed to engine oil fumes.

Some people who have been exposed to the chemicals from engine leaks have complained of long-term neurological effects, including tremors, memory loss and loss of vision. A pair of twins who were passengers on a Southwest flight have sued the airplane manufacturer. A former flight attendant is also involved in litigation against Boeing.

(Boeing told our news partners at KING5 in Seattle that cabin air in airplanes is safe. )

Alisa Brodkowitz, who represents the plaintiffs in both suits, says the airlines and airplane manufacturers have simply refused to act.

They have the science to monitor bleed air contamination on these planes, and they are not doing it. They have the science to install sensors on this aircraft, and they are not doing it, Brodkowitz told NewsChannel 36. This problem has been kept under the radar screen. Passengers are exposed to fumes and become sick on a flight and they scatter to the four corners of the world and no one ever tells them why they may be sick.

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