Toxic fumes are elusive and dangerous - Curt Lewis

Airline crews are worried about toxic fumes on board

When several people fell ill two hours into American Airlines Flight 109 from London to Los Angeles on Jan. 27, the pilots turned the plane around.

Aboard the Boeing 777, one flight attendant had collapsed in the aisle while other crew and passengers felt faint, according to witness accounts. When the plane landed in London, emergency crews offered medical assistance and ran tests on the air - but the cause of the illnesses remains a mystery.

"We found no issues with the aircraft," an American Airlines spokesperson said.

"Our maintenance team conducted a thorough inspection of the aircraft, including a test flight, and found no issues with the Boeing 777-300. Out of an abundance of caution, all of the air filters on the aircraft were replaced." The plane was soon back in service.

That doesn't mean the issue is resolved - at least for many airline employees.

Mashable's conversations with a dozen crew members at major airlines in the U.S. and Europe revealed frequent concerns about cabin air safety that go far beyond a single airline. Stories of strange smells - resulting in symptoms like headaches, nausea, memory loss and tremors - suggest a rare but potentially dangerous phenomenon.

Despite their fears, the employees can't prove it: Airlines and aircraft manufacturers say the air in planes is safe.