KEY POINTS:
You reserved your seat on the plane months ago, you've checked in hours ahead of time and you are carrying only the absolute essentials: handbag, book, a couple of muesli bars and an extra magazine just in case. After all, there's only so much room to go around.
But when you finally get on board, you find yourself next to someone so big, so oversized, that he not only completely fills his own space but spills into yours as well
That's what happened to David Smith (like other passengers in this story his name has been changed) on a British Airways flight from Rome to London.
"Sure," he says, "it wasn't that long a flight, only three-and-a-half hours." But it was also the first leg of the long journey back to New Zealand, with another 22 hours still to come, and he really needed to rest.
Unfortunately the woman next to him was so large her bulk bulged over and under the armrest into his seat, making any chance of sleep impossible. "She took a good quarter of my seat."
As a result, Smith was forced to sit at an awkward and uncomfortable angle. By the time the flight was over, his neck was out and his back was aching.
"I did try to move. I discreetly explained my situation to the flight attendant but was told there was nothing she could do. It was very frustrating."
Karen Kennedy agrees. On a trip to Canada, she estimates that on half of her flights, she was seated next to overweight passengers.
"It's getting more and more common," she says. "And if a flight is full, most airlines have not a single procedure in place to rectify the situation to the satisfaction of both persons involved.
"It's not good enough that I should pay for a seat that I am not able to fully occupy."
Kennedy thinks she's entitled to some compensation for only having the use of half a seat, and wonders whether passengers who take up more than their seat should be required to pay extra.
"One of the airlines in the US does that," she says, "though I hear the policy is not without controversy."
That airline is Texas-based low-cost Southwest, which has been in business for more than 35 years and flies more than 80 million passengers a year.
In 2002, Southwest instigated a "customer of size" policy for larger passengers. According to a company spokesman, the policy has been in place since 1980 but was only recently enforced.
"We could no longer ignore complaints from customers who travelled without full access to the seat purchased because of encroachment by a large seatmate whose body extended into the neighbouring seat."
The company website states the policy does not focus on weight but size. If a passenger's girth extends beyond the seat cushion, he or she is required to purchase an additional seat. "We use the ability to lower the armrests as the gauge, as the armrests are truly the definitive boundary between each seat."
But, as David Smith argues, this is not always the case. "Some people can lower the armrest and still infringe on their neighbour."
Smith feels so strongly about the issue he raised it with British Airways but feels his complaint was not taken seriously. "I got a letter back but I wasn't happy with that. The more I thought about it, the more I felt like I should receive a refund of some sort."
When he followed up, he says, the airline ignored him. To date, five months later, he has yet to hear back.
So how do the airlines deal with the issue? Air New Zealand spokesperson Rosie Paul says "like other airlines and, indeed, most enterprises that provide customer seating as part of its product offering, we have no specific policy which identifies special treatment or an additional charge based on a person's weight."
Qantas customer care executive Luella Parr says it is "difficult to anticipate situations like this because the first time we see a customer is at the check-in, by which time seats on the flight are already allocated. We also have to keep in mind our obligations under the discrimination laws."
Air Canada, which Karen Kennedy contacted after her unsatisfactory flight, states it cannot force a passenger to purchase an extra seat.
Unlike Southwest, Canada's national airline appears not to use the armrest as a gauge but rather the seatbelt extensions. If the seatbelt plus extension does not fit, passengers are given the option of purchasing another seat or not travelling.
But is requiring obese passengers to buy two seats the answer? Lynda Finn, author of Largely Happy, founder of the New Zealand support group Wide and Wonderful and co-chair of the International Size Acceptance Association, believes airlines are to blame for this increasing problem.
"Almost everyone I know complains about the cramped conditions in aircraft," she says. "Why? Because these planes have been designed to cram in as many people as possible and when the designers were at the drawing board, they used the calculator rather than common sense.
"It's not just overweight people who suffer but tall passengers, too. Many men, regardless of girth, are above average height but is any attention given to the fact they cannot get their legs comfortably into airline seats?"
Finn says that until airlines realise bigger people are here to stay, and design aircraft seating accordingly, they are going to cause friction.
But airlines like Southwest claim that's easier said than done: "Our ongoing goal is to operate a low-fare, low-cost airline, and the costs of reconfiguring our fleet would be staggering and would ultimately reflect in the form of higher fares for our customers."
Linda McKay-Panos is one airline passenger who has bought a first class seat just so she could sit comfortably while flying.
Required to travel from Calgary to Ontario via Toronto, and having put on weight because of a health condition, she was concerned about fitting into the seats and sought advice from Air Canada.
The airline told her it was not necessary to buy two seats and tried to deal with the problem by seating her behind the bulkhead. That only made things worse because those seats have thicker armrests, where the tray tables are stored.
As McKay-Panos feared, the seat was unable to accommodate her; she was spilling over into her neighbour's space and "the flight attendants kept bumping into me with the cart".
Her return flight was no better, she says, despite having called the airline and been assured of no repeat performance. So during a stopover in Toronto she bought a first class ticket.
The 49-year-old lawyer and Executive Director of the Alberta Civil Liberties Research Centre of the University of Calgary filed a complaint with the Canadian Human Rights Commission, which was then transferred to the Canadian Transportation Agency (CTA). She lost.
McKay-Panos wasn't deterred. In January last year, she won an appeal to the Federal Court of Appeal. "I am still working on my case and may be for several years to come."
Meanwhile, the fact remains people are getting heavier. The average adult now weighs 11kg more than in 1960. And that's a problem for airlines.
In the United States, where 65 per cent of the adult population is either overweight or obese, a government study found that in the year 2000, American airlines used an additional 1.3 billion litres of fuel to carry the load, resulting in an extra 3.8 tonnes of carbon dioxide emissions a year.
In 2003, the crash of a commuter plane less than a minute after takeoff in North Carolina, killing 21 passengers and two crew, was blamed on a maintenance error and the number of overweight passengers in the back. Nor is it a uniquely American phenomenon. The latest obesity report from the World Health Organisation estimates that the countries with the highest proportion of obese people are - in this order - Nauru, Micronesia, Cook Islands, Tonga, Niue and Samoa.
The US was 9th on the list, New Zealand was 17th and Australia 21st.
In other words, if you go by plane in this part of the world there's an increasing likelihood of having on obese neighbour.
But while some airlines seem to be tackling the issue of legroom, few appear concerned about seat width. Maybe that's because customer research by airlines indicates that for flights less than six hours, passengers are more concerned with scheduling, fares and getting optimum frequent flyer points for their dollar rather than relaxation.
Only on longer flights does comfort become a significant priority. And apparently the most important factor in determining passenger perception of comfort is not one's own seat but the one next door and whether or not it is occupied.
Linda McKay-Panos can sympathise. She felt terrible for imposing on her neighbour's space on that long ago dreadful flight.
But, she says, that does not excuse the manner in which she says she was treated. "People who are obese deserve to be treated with dignity and respect."
And Lynda Finn says forcing larger passengers to fly first/business class or to buy two economy seats is not the answer. "If you set your self up to provide a public service, then as far as possible, you should do so. All shapes and sizes need to be taken into account.
"Airlines may kick and scream and charge fat people double the fare now but this won't last. Airlines need to rethink their strategy and start catering for as many people as can pay and that includes the extra tall and the extra large."
So what is the answer? A special section just for fat people, with bigger wider seats? "Absolutely not," says Finn. "It's ludicrous!"
Bigger wider seats for all? "Well, sure, that sounds nice," says David Smith. "But then that means fewer seats can fit on the plane. Less seats mean less passengers, less passengers means less revenue.
"So how would the airlines make it up? By increasing fares. I doubt you'll find many people happy with that."
THE AIRLINE SEAT WEIGHTING GAME FROM BOTH PERSPECTIVES
Rachel Wright, 29, structural engineer, New Zealand Weight Watchers Slimmer of the Year 2006 after losing 54kg over 21 months :
I can sympathise with the overweight passenger having been one myself, but after losing my weight I have to admit that my opinion has probably changed from what it might have been a couple of years ago.
Generally speaking I think that people need to take responsibility for themselves, their actions and their health and well-being.
If they are uncomfortable in a single seat on a plane, whether overweight or tall, they have options - flying in business class or purchasing the adjacent seat, which would put the cost of the problem on to the passenger.
The difficulty here is that it relies on that person's allowable comfort level, but people have different tolerance levels, and the person adjacent to them can suffer as a result.
This is no different really to sitting by someone on a plane who is sick, or drinking too much and being loud and annoying or reading with a light on during an overnight trip when you are trying to sleep.
Personally I found flying an uncomfortable experience.
I did not spill over on to the next seat but there was no spare space and I was jammed in between the armrests.
My husband, who is tall and slim, would suffer from a lack of legroom but was not bothered by my size sitting next to him.
I am conflicted with the idea of measuring people up once they are at the airport, which is effectively what they are doing with the armrest test.
Had that happened to me when I was overweight I would have been mortified.
After someone has felt very conscious of their weight for a while it is often an experience like this that is all it takes to encourage them to make some changes. But everyone is different.
Ultimately, I fear that if the airlines reduce the number of seats and make them larger it will just be another step towards obesity gaining national acceptance - as opposed to finding solutions and getting the problem under control.
