The policy applies to customers who bought tickets on or after April 1, 2020, and who are looking to swap over to a flight of equal or less value.
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.
Airlines are following face-covering recommendations by the U.S. Centers for Disease Control and Prevention.
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."
Passengers on a Mother's Day Alaska Airlines flight ended up being part of its history.
"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.