With in flight refuelling and a mechanism for the plane to also be able to take on fresh hostess trolleys and new supplies of consumer goods, the plane could stay in the air until it fell to bits. In time a viable society could develop. So what would it be like this airbourne society.
Communication with the outside world, since the use of mobile phones on planes is not allowed, would be limited to the pilots radio. The society would effectively be isolated and could quickly develop in unusual ways. For example, it is obvious that environmental issues would quickly become noticed and would be more easily diagnosed than in a society which is less closely pressed. Flatulence and body odour could critically damage the fragile eco-system within a short time and would have to be dealt with firmly - perhaps by ghettoisation of the perpetrators or maybe even harsher measures.
It is safe to assume that no significant agriculture could take place aboard even the roomiest of aeroplanes. Given also that meals would regularly be delivered and the extremely poor quality of farming land it would seem that such projects would have to be limited to small amounts of cress and mustard seed grown on carpets near the exits and watered with bottles of mineral water. Possibly, projects involving growing mushrooms in the overhead lockers might be undertaken but, given the limited nature of the locker space, and the fact that only human manure would be available as a fertiliser, this would probably only take place in the poorest areas of the plane (very likely the smoking section at the rear).
It is practically certain that large scale industrial processes would be out of the question. It is hard to see how even the simplest manufacturing could take place. However, with the limited range of available products it is possible that "cottage industry" could thrive. For example, someone who could sew silk scarves together into workable shirts would be in great demand as the passengers' original clothing began to wear out. Although footwear would be extremely long-lasting in such a society, it is also not outside the bounds of reason to suppose that manufacture of new shoes, perhaps from "hand-tooled leather handbags available from the trolley", could take place. It is also certain that, in a society which spends almost one hundred percent of its time sitting, posterior comfort would be a vital issue. A craftsperson who could turn "Timmy the cuddly Tiger" into a soothing orthopedic cushion would find their skills much in demand and could make a tidy profit.
Trade would of course be an important part of the plane society. For a society born of the airport, novels by authors other than Stephen King and Barbara Taylor-Bradford would be worth more than gold. Entertainment items would also be a boon - on a plane with piped easy listening music, even an aged, poor-quality, pirate recording of a Smiths album could be worth a small fortune to the right buyer.
Of course no society can survive solely by internal trade and it is in the field of service industry that the plane society would truly thrive. When the average living space is of the order of a few cubic metres, counselling would be a skill much in demand and a trained therapist could soon find themselves extremely rich. Of course, the extreme wealth differences which would result as most of the voyagers found themselves sacked for chronic absenteeism, would create certain passengers who had greater economic leverage. This would enable them to hire services, and perhaps land, from other passengers. For example, in a society with so much leisure-time, it may be important to them to have a custom-written game of tetris for their portable computer, or a hand embroidered cover for their fold down table.
The balance of trade would quite important to the plane society. Initially, the society would be made viable by the passengers' continuing to be paid and therefore being able to buy raw materials from the airline company (from the wide range available in their fascinating in-flight catalogue containing a huge selection of quality goods). Later, as this influx of external money dries up, the society would have to consider exporting. It is hard to know what of value they could give to external society, however, it is plausible, to me at least, that even short descriptions of life on board could be of extreme value to psychologists and sociologists everywhere. Perhaps this might be enough to maintain a balance of payments with the extra-plane world.
The heavenly hierarchy seems to be obvious. The pilots, unseen, all- powerful, controlling the destiny of the whole plane, would clearly be the godhead. The flight stewards and stewardesses, who can make contact with the godhead and who move from place to place rather than settling in one place like mortals, are a clear manifestation of the angellic host. As the original purpose of the flight became lost, the destination of the plane would take on mystical significance and could, perhaps, be identified with the afterlife or promised land. It is hard to know what Manchester Airport can be said to be flowing with that is in any way desirable, but, as tales of it were handed down from generation to generation, it may even be possible that it would be considered a good place to get to.
Sculpture would, perhaps, be the first art-form to be developed, growing out of novel arrangements of plastic containers from in-flight meals. In the limited confines of an aircraft seat, large installment pieces would be unfeasible but small sculptures such as could be displayed on a fold-down table or dangled from an overhead locker would undoubtedly be popular and might even come to be seen as a status symbol with pieces being commissioned from particularly skilled artists.
Painting, as such, would be impossible due to a lack of canvass and materials but perhaps table-back decoration, with biros and marker pens could become a significant new art form combining elements from graffitti, cave-art and interior decoration. The choice of subject matter would be interesting. Would artists choose to paint from memory or devote themselves to cloud studies and portraits of other passengers?
It is perhaps in the area of literature that the plane society would excel. Given such a large amount of leisure time and time for thought and reflection, it is possible that large-scale reflective works would make Proust's total output seem terse. However, such literature would doubtless grow from forms of writing which the passengers were more familiar with, for example postcards and internal memos. The nature of these forms of communication extended to novel length would make for an intriguing, if at times frustrating, read.
Sexual mores would be important for a society like the plane society which would almost certainly place great value on the limited privacy available. To my mind, having sex under the blankets provided by the flight-staff would be considered the height of bad manners, particularly in areas where three people are on the same row (assuming only two of them are engaged in the aforementioned intercourse). It seems likely that the toilets would become a focus for sexual activity and indeed it could be that the very toilets themselves will become suffused with a certain sexuality-by-association.
Given the lack of other recreational facilities and the fact that in-flight trolleys do not sell contraceptives, it seems likely that there would be an initial "baby boom" after the first nine months of the flight (even given the generally low female to male ration on such planes). This population expansion would have to be carefully controlled since the resources of the plane would be extremely limited especially with regard to living space.
The plane society, with its largely sedentary population, high stress and poor diet, would be accutely conscious of the fact of its own mortality. Life expectancy would be, for some, small. It is hard to know quite how the society might deal with this. I fear it may be, considering the lack of fresh meat, that cannibalism is a possibility. If this contingency is avoided, it could be that the corpses would be ceremonially thrown from the rear exit (obviously after the plane has descended some way to avoid depressurisation problems). In this way, they would symbollically be reunited with the promised land "Terra Firma".
As generations rose and fell, it would in time become necessary to replace the pilot and co-pilot. It seems logical to me that the brightest and most-promising of each generation would be chosen for this most sacred of tasks and would be taken up to the godhead to live amongst them for their training.
Later still, the memories of "land" would distort being passed on down by word of mouth and generations would have to rely on on-board literature for the "truth" about the "land-dwellers". Given that the on-board literature would have been purchased at air-ports and would largely consist of Stephen King and Barbara Taylor-Bradford novels it is hard to know what they would make of this. Perhaps some thinkers would come to reject the very idea of the existence of "land" as a myth which was created to oppress and force them to conform to societal norms.
Eventually, a renaissance of sorts may occur on board with projects undertaken to discover the nature of the universe and the very essence of the plane and it is these very investigations which will spell doom for the plane society as an early free-thinker begins to conduct experiments into "the aerie and fantastick nature of the interiore of the fuele tankes".