Mysterious Odor on Alaska Airlines Flight Causes Diversion, 12 People to Be Treated for Breathing Issues

An Alaska Airlines flight from Chicago to Seattle was grounded yesterday after crew members said an odor had caused breathing issues in the cabin.

The plane was diverted into Minneapolis-St. Paul International Airport, where half a dozen crew members and two passengers had to be given a medical checkup. Four staffers were taken into hospital. It remains unclear what the odor was. Officials said the case is now under investigation.

Alaska Airlines Flight 51 departed from Chicago O'Hare at 5:48 p.m. local time. It was forced to land as a precaution just before 7:20 p.m. local time, officials said.

In a statement to NBC News, Minneapolis-St. Paul airport spokesperson Patrick Hogan said some of those affected complained of respiratory issues. There were 144 people on the plane.

"Six crew members received a medical evaluation at the airport and four were transported to the hospital for further evaluation," Alaska Airlines said in a statement provided to KSTP-TV, a media outlet based in Minnesota. The issues were not limited to staff, officials noted.

"Two passengers were also evaluated at the airport," the statement continued. "The cause of the odor is being investigated and the plane has been removed from service pending an inspection. The flight has canceled and passengers will be rebooked on a different flight to Seattle."

The plane was a Boeing 737-900, NBC News reported.

It was not the first odor incident for Alaska Airlines this week. On Tuesday, a flight had to return to ground for the same reason, KARE11 reported. Three crew members were taken to hospital.

The airline told USA Today: "Flight 1506, an Airbus aircraft, departed Seattle-Tacoma International Airport for Orange County at 9:06 a.m. During the flight, the crew reported a cabin odor. As a precaution, the aircraft returned to Sea-Tac at 9:40 a.m.

"The pilots and flight attendants received a medical evaluation at the airport, and were then transported to the hospital for further evaluation." No passengers needed medical care.

In August last year, an Alaska Airlines flight from San Francisco to New Orleans was diverted to Los Angeles International Airport after a "strong odor" was detected on board. "The cause of the odor is believed to have emanated from someone or something in the cabin," officials told Newsweek at the time. A total of 136 passengers were rebooked on replacement flights.