Image caption Air Samoa said the policy meant some people would end up paying less to fly

The head of Samoa Air has defended the airline's decision to start charging passengers according to their weight.

Chris Langton told Australia's ABC Radio that it was "the fairest way of travelling".

Rather than pay for a seat, passengers pay a fixed price per kilogram, which varies depending on the route length.

Samoa Air flies domestically and to American Samoa. It is thought the move could encourage other airlines to introduce similar policies.

"Airlines don't run on seats, they run on weight, and particularly the smaller the aircraft you are in the less variance you can accept in terms of the difference in weight between passengers," Mr Langton told ABC radio.

People generally are bigger, wider and taller than they were 50 years ago Chris Langton , Samoa Air boss

"Anyone who travels at times has felt they have been paying for half of the passenger next to them."

Under the new model, Mr Langton described how some families with children were now paying cheaper fares.

"There are no extra fees in terms of excess baggage or anything - it is just a kilo is a kilo is a kilo," he said.

Air Samoa's rates range from $1 (65p) to around $4.16 per kilogram. Passengers pay for the combined weight of themselves and their baggage.

Mr Langton also suggested that the move had helped promote health awareness in Samoa, which has one of the world's highest levels of obesity.

"People generally are becoming much more weight conscious. That's a health issue in some areas," he told ABC Radio.

Mr Langton said he believed that charging by weight was "the concept of the future."

"People generally are bigger, wider and taller than they were 50 years ago," he said. "The industry will start looking at this."