An American Airlines plane has had to be diverted after four passengers fainted and flight attendants complained of dizziness.
The flight made an emergency landing at Dayton, Ohio, after a suspected problem with the air conditioning system.
It's thought passengers may have suffered 'aerotoxic syndrome' - an illness caused by airplane passengers breathing air that becomes contaminated with a cocktail of chemicals from the plane's engines.
People started complaining about the air quality at about 28,000 feet.
Aside from those who fainted, several others reported feeling sick and being on the verge of vomiting, while one passenger reportedly had an asthma attack.
Christina Saull, a passenger from Washington, told the Dayton Daily News that before the plane took off there was an announcement made about problems with the air and cabin pressurisation system.
She told the Daily News: 'Halfway through the flight, the woman in the row behind us ... we thought she had a seizure.'
Really she and the woman next to her had passed out. Then passengers ten rows up complained of fumes and feeling light-headed.
The plane landed safely at around 8.20am. Within half an hour the 126 passengers and six crew had left the aircraft.
At least two passengers were taken to a local hospital for treatment, and medics from three towns were sent to the airport.
Passengers were kept in the American Airlines holding area at the airport, while the airline made alternative arrangements.
Video: Passengers tell of panic as roof of plane rips off mid-air
Ten ways to tell you're an annoying air passenger
Have you ever experienced 'aerotoxic syndrome'? Let us know below...