American Airlines Flight 109, traveling from London to Los Angeles, was two hours into its flight when passengers and crew members suddenly started fainting or otherwise becoming ill. The captain turned the Boeing 777 around and landed at Heathrow.
According to the Daily Telegraph in Britain, the aircraft likely experienced a problem with the aircraft's pressurization system:
This would suggest problems with cabin pressure, although normally such problems occur during take-off and landing.
American Airlines added that the aircraft was being inspected by maintenance engineers.
Actually, what happened was likely a “fume event.” For years, the airline denied fume events existed, but now we know that they do. And we know that they are dangerous. In fact, I wrote about a fume event aboard another American Airlines Flight (Flight 49) almost five years ago.
Here's what happens: airlines pump air into the cabin. The air is a mix of fresh air and air that has been compressed by the aircraft's engines--known as "bleed air." But when the air distribution system malfunctions, toxic chemicals found in the aircraft's engine oil can be heated and pumped through the airplane, creating a fume event that makes passengers sick
Sometimes the passengers recover quickly, sometimes the ill effects can linger for years, with victims suffering ongoing tremors, memory loss, and headaches.
If they are injured, passengers can recover against the responsible airline. Because American Airlines Flight 109light was international, the Montreal Convention applies. The Convention requires an airline to offer fair compensation to anyone injured as a result of an "accident." A fume event would likely qualify as an accident, even though some airlines now contend that fume events are a "normal” part of flight.
The flight attendants, however, can't sue the airlines due to workers' compensation laws. That means their only chance for compensation is a product defect claim against Boeing, the aircraft's manufacturer. As it turns out, Boeing has known about the risks of fume events in its designs since the 1950’s.