A pair of American Samoan businessmen have filed complaints to the US Transportation Department after they were weighed before boarding a flight from Honolulu – and assigned specific seats to keep the aircraft’s load evenly distributed.

Radio New Zealand reports that Hawaiian Airlines – in response to an increase in average passenger weight – has been routinely preventing those flying to or from Pago Pago, the capital of American Samoa, from choosing their own seats online, and has also required them to step on the scales before boarding.

Fuel burn on American Samoa flights was consistently much higher than projected Hawaiian Airlines spokeswoman

The airline told the station that the expanding girth of the typical passenger means it is required to redistribute weight in its Boeing 767 cabins to meet the manufacturer’s guidelines. This means limiting the number of adults per row and reserving seats in certain rows for young children, the broadcaster's report said.

American Samoa Credit: sorincolac - Fotolia

But Avamua Dave Haleck, one of the two businessmen to have taken action, believes the new rules are discriminatory because it only applies to those flying to or from American Samoa.

Radio New Zealand also pointed out that a Boeing 767-300, used on the Honolulu-Pago Pago route, can safely fly 269 passengers a distance of 11,000km, while the distance between the two cities is just 4,176km.

"Hawaiian is saying that it is a safety issue,” said Mr Haleck said, "so have we been flying unsafe for all these years?”

The move, it has been suggested, may be driven by the fact that American Samoa, according to the CIA’s World Factbook, has the highest rate of obesity in the world. A remarkable 74.6 per cent of its adult population are considered obese, it says, placing it above Nauru (71.1%) and the Cook Islands (63.7%). Those are figures for 2007 and 2008, however. More recent estimates claim the obesity rate could now be as high as 94 per cent.

A Hawaiian Airlines spokeswoman told Telegraph Travel that the practice of weighing passengers on the route was carried out as part of a six-month survey, which recently ended.

"This action resulted from the recognition that over time our fuel burn on Pago Pago flights was consistently much higher than projected, indicating that our weight assumptions were inaccurate," she said. "We review weights on any flight within our route network that demonstrates such a discrepancy. For example, we surveyed our Japan and Korea flights in 2015 and our new Narita flight earlier this year.

More than half of Telegraph Travel readers think overweight fliers should pay more Credit: ALAMY

"The survey results confirmed that our aircraft cabin weight was heavier than projected. This requires us to manage the distribution of weight across each row in our cabin and we have elected to do so by making sure that one seat in each row is either empty or occupied by a traveller under the age of 13.

"The decision to assign seats at the airport was made because that is the most efficient way to manage weight distribution. This allows us to make sure that families with children are seated together, for example, and it minimizes the confusion created by changing pre-selected seats."

The US Transportation Department said it is investigating the complaints against Hawaiian Airlines.

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In 2013, Samoa Air became the first airline in the world to charge passengers according to their size. Those flying on the South Pacific carrier, which largely operates domestic routes, were asked to pay one Samoan tālā (around 29p) for each kilo that they, combined with their luggage, weighed. The policy received the backing of more than half of Telegraph Travel readers.