A decision by Samoa Air to charge customers based on their weight has sparked fears that it will punish people who cannot control their size.
The airline says it is the first in the world to adopt the policy, charging passengers according to the total weight of themselves and their belongings.
Rates vary from WST$1 (NZ$0.52) a kilogram on the airline's shortest domestic route to NZ$2.32 for flights from Samoa to American Samoa.
"This is the fairest way of travelling," Samoa Air chief executive Chris Langton told Australian media.
"There are no extra fees in terms of excess baggage or anything - it is just a kilo is a kilo is a kilo."
Norwegian professor Bharat P Bhatta has sparked controversy after suggesting that airlines should charge passengers based on weight as a way to accommodate rising fuel prices.
But Carolyn Costley, a morals and ethics professor at Waikato University, said such a practice could lead to discrimination.
Smaller planes used to weigh passengers in the same way but used the information to factor in how much baggage they could take, she said.
"It's not collecting the information that's the problem, it's what you do with it. It leads to a price discrimination against overweight people," she said.
"Would this encourage lighter people to fly more and larger people to fly less? It becomes a punishment on people who may not have control over their size."
Samoa Air requires passengers to enter an estimated weight of themselves and their baggage when booking. This is then verified at the airport, making customers the "master of how much your air ticket will cost", its website says.
Air New Zealand would not comment yesterday on the possibility of charging by weight.
Jetstar said it had no policy about larger customers, but they could buy an additional seat if they wished. The airline also offers free seatbelt extensions.
Virgin Australia said it aimed for comfort and did its best to seat larger passengers next to an empty seat, or offer to move them to another flight at no cost.
Waikato University dean of law Bradford Morse, who specialises in human rights law, said it was "definitely a tough issue" that was not as straightforward as some might think.
He cited a discrimination case in Canada, now before the Human Rights Commission, against airlines that had started to charge larger passengers for two seats.
"You can see where airlines are coming from. People who are large make it impossible to seat a person next to them, and more weight does mean more fuel consumption," Professor Morse said.
"There's also the public health argument that we should take all avenues of encouraging people to lose weight."
Legally, it was discrimination only if the extra fee was based on obesity, which was arguably a disability, he said. But if the fare was tied only to weight, then it was fair game.
"Airlines have been boosting ticket and baggage prices recently to accommodate for those fuel costs . . . next we could easily see extra charges for people with physical disabilities, who require extra help and time . . . boarding," Prof Morse said.
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