Alaska Airlines Flight 422 was forced to return to Seattle-Tacoma Airport shortly after a male passenger was filmed saying he would "kill everybody" on the plane.
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Half a dozen crew members had to be given a medical checkup after the plane was grounded.
"We are reviewing what transpired with our Piedmont and Kansas City colleagues," the airline said.
The aircraft was carrying 136 passengers from San Francisco to New Orleans when the mysterious smell forced an unscheduled stop.
"I cannot believe that an airline in this day and age would give a straight couple preferential treatment over a gay couple and go so far as to ask us to leave."
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"If a non-disabled child that threw up, would the airline have kicked that family off the flight?" Meaghan Hess asked.
"The pilot said he didn't want it around his feet. Maybe he had a phobia?"
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Upon hearing unusual noises, the pilot requested an emergency landing and returned to Seattle.