Officials at SkyWest Airlines and federal authorities say they still don't know what caused three passengers to lose consciousness on a flight that then made an emergency landing in Buffalo Wednesday. Earlier, the airline said one passenger was affected.
The SkyWest plane, operating as United Express flight #5622, was flying from Chicago's O'Hare airport to Hartford, Connecticut with 75 passengers on board.
Some passengers say part way into the flight, they started having trouble breathing, and felt dizzy and nauseous.
Mary Cunningham, a nurse who happened to be on the flight, told WFSB TV that she was asked to help one sick passenger.
"By the time I saw her, she was pretty lethargic, her color looked awful, so I asked for some oxygen for her and once she had oxygen, she was looking a lot better, responsive, and then all of a sudden, the woman behind her passed out," said Cunningham.
The crew then decided to divert the plane to Buffalo in a rapid descent from its cruising altitude of 37,000 feet. Once on the ground, emergency medical personnel treated 14 passengers and one crew member who reported symptoms, including the three who lost consciousness.
None was hospitalized and all eventually went on their way to Hartford.
A spokesman for SkyWest says maintenance crews and mechanics checked out the plane and found no evidence of any problems with the air pressurization, ventilation or other systems.
Spokesman Wes Horrocks told NPR's David Schaper the cause of the illnesses remains a mystery.
The aircraft, an Embraer E170 jet, remains in Buffalo as of late Thursday but Horrocks says it has been cleared by mechanics to return to service. A crew will fly the plane back to Chicago before any passengers board it again.
The Federal Aviation Administration is investigating the incident but has offered no new information about what may have caused the inflight illnesses.
The National Transportation Safety Board is aware of the incident but has not opened an investigation into it. "We're trying to understand the circumstances before we decide what if any action we would take," NTSB spokesman Eric Weiss told the AP.