Monash University research shows a high proportion of overweight airline passengers buy two seats to save themselves embarrassment.

One frequent flier suggests the aviation industry, especially given its current downturn, should be doing more to accommodate obese fliers.

Terry, who has struggled with obesity for the past 15 years, flies about twice a month.

"I get an aisle seat, because that gives me room for overhang, let's put it that way," he said.

"And it certainly becomes a very intimate exercise if someone who's also obese is sitting next to me; but we make allowances for each other."

He says he has never offered to pay for two seats, nor will he.

"Why should I? It's not my fault that the airlines made the seats so small. I'm not two people," he said.

"That would be highly discriminating, obesity is a functional disability.

"Do they ask people who have to be put on plane by forklift to pay for the forklift if [they] have a wheelchair?

"If people have small child, where they use a bulkhead cradle for that child, are they expected to pay extra for the bulkhead cradle?"

Terry cites airlines, theatres and clothing stores as three offenders which have failed to adapt to society's obesity problem.

"There's a large minority of people who are overweight or obese. It is a social problem," he said.

"There are sometimes medical reasons why people are overweight or obese, but it's something which is now very common in society.

"It's regrettable that's the case but it's a fact of life and I think we need to adjust as a society to this."

Embarrassment, discrimination

Monash University health sociologist Dr Samantha Thomas has been researching discrimination felt by obese people, especially on planes.

"Quite often an obese person will have to ask for an extension seat for their seatbelt and quite often they are met with some very disparaging or embarrassing remarks like it's a hassle for the cabin crew to go and get a seatbelt extension for them," she said.

"The second thing we find is that quite often normal-weight passengers will quite overtly say they don't want to sit next to a fat person on the plane, that they're physically uncomfortable because of it, that they don't want to and that the person should be moved."

Dr Thomas says many choose to fork out more money for two seats, to pre-empt embarrassment.

"What we've found is that either the airline industry will stop them from buying two seats or when they come to board the plane, they'll find that the two seats that they've been allocated are in vastly different sections of the plane," she said.

"So no matter what people try to do to overcome this, they're still faced with that level of embarrassment when they fly."

Dr Thomas says it is hard to know how to deal with the discrimination some people face.

"How do we judge how fat is too fat? What we know about our measurements of obesity is that actually if we took those same measurements and applied them to some of our elite athletes, our rugby players or our AFL players, they'd be judged to be fat as well, which obviously is not the case," she said.

"What do we do if we're publicly and openly humiliating fat people on a plane, do we do the same to thin people?

"Do we say, excuse me Mr Smith in seat 10C, you've been judged to have been half the size of all your fellow passengers, so we're going to give you a 50 per cent discount?

"It's really unfair and the overt way in which they do this is quite unacceptable."

Weight policy

Dr Thomas says of all the airlines, her interviewees say they have had the least problems with Jetstar.

Jetstar's Simon Westaway says where possible, it tries to allocate overweight passengers a seat next to a vacant one. Otherwise it encourages them to purchase two.

"It's not implicit, but if a customer wishes to purchase additional seat they can obtain that additional seat and at time of check-in they're allocated the two seats they've purchased and we just consider it like a second customer travelling," he said.

"From our perspective we've had the same policy for over five years."

Mr Westaway says Jetstar has people regularly purchasing extra seats.

"We do have regular customers who book additional seats for themselves for extra comfort," he said.

"The reality is no court in Australia has proven that obesity is a disability.

"We acknowledge that there is an ongoing debate around this; different countries and different jurisdictions are going down a certain path from the Australian experience. We think the way that Australian airlines operate encourages choice."

Terry, however, says airlines should work around passengers, not the other way around.

"I will vote with my feet or with my bottom if airline chooses to make it compulsory to buy two seats because I'm overweight. I'll go to those airlines that don't," he said.

Based on a report by Rachael Brown for PM, which aired on Friday, April 17.