Crew members from three previous flights of the US Airways plane that made people sick this week in Charlotte still have not returned to work because of illness related to those flights.
Researchers say passengers on those previous flights might have unknowingly been exposed to toxic fumes, and symptoms might not show up for days or weeks.
Eight pilots and crew members on flights in December and January have not returned to work due to their symptoms, a flight attendant union representative said Wednesday.
"They're all breathing in the same air," said Judith Murawski, a safety researcher for the Association of Flight Attendants. "There's no question that passengers might be affected, and they just have no idea."
U.S. Airways spokeswoman Michelle Mohr said Wednesday that passengers on at least one of the previous flights - Flight 1041 from St. Thomas, Virgin Islands, to Charlotte on Jan. 16 - were notified of possible exposure.