Mary Cunningham, a passenger and registered nurse, said she helped another passenger who passed out and had "awful" coloring.
"I went back to my seat after she was feeling better, and all of a sudden, the woman sitting behind her passed out unresponsive," she told NBC Connecticut.
Cunningham said she was soon affected, too.
"I felt very nervous. I realized something was very wrong, and it was really scary," said Cunningham. "That was terrifying."
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