United Airlines says it will start charging passengers who can't fit in a single seat, can't properly buckle the seat belt using an extender, or who can't put the arm rests down when they're seated.
It's not sitting well with everyone, reports Mike Sugarman, of CBS station KPIX-TV in San Francisco.
United would join a handful of other airlines that could end up charging you for two seats.
It's for the other passengers' comfort, the carrier says, citing 700 complaints last year about uncomfortable rides next to large people.
"I think it's probably a sensible thing to do, because I've had some very unfortunate journeys back and forth from the States when I just sitting in a two-seat row with someone who is taking up three fourths of that space," said Daniel Evans, a passenger.
United didn't return Sugarman's phone calls.
But people of size say they're appalled.
"Who makes the chairs? United. Who gets the money? United," said Marilyn Wann, an activist for overweight people.
"If a fat person buys a first class ticket, the extra width of the chair is taken up by that little console," she said. "So basically, the airlines build the chairs and airplane to say we don't like fat people here -- and that's discrimination."
"What you are going to be charged for when you get there shouldn't be a surprise," asserts attorney Alexander Anolik, who wrote the book on travelers' rights.
"Subjectively, to say, 'I'm going to eyeball you, turn around, you're going to pay for two chairs'? That's terrible," said Anolik.