An American Airlines flight from Brazil to Miami was diverted Friday after a passenger and three flight attendants complained of lightheadedness, according to the airline.
It's the second incident of its kind in as many days.
Flight 904, which departed Rio de Janeiro with 203 passengers and 14 crew members on board, landed safely in Brazil's capital and was met by paramedics. The passengers and crew were evaluated by medical staff, but none sought further medical treatment, an airline spokesperson said.
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The flight was canceled "out of an abundance of caution" and passengers were booked onto other flights, the airline said.
Maintenance crews are inspecting the aircraft and performing a maintenance check.
It's the second incident of its kind this week. An American Airlines flight from London to Los Angeles was also diverted Wednesday under similar circumstances.
American Airlines Flight 109 from Heathrow to LAX doubled back after a "medical emergency" occurred on board, airline officials said. Two passengers and several crew members also complained of lightheadedness during the flight.
According to The New York Times, such symptoms have been linked in the past to contaminated cabin air, known as aerotoxic syndrome.
No maintenance issues were found on Flight 109, but the plane's air filters were changed as a precaution, the airline said.
It is unclear in either incident what caused passengers and crew to become ill.