Geneva - Fighting soccer fans, fashion models screaming obscenities and a French film star relieving himself in the gangway are just a few well publicised examples of what airlines say is a growing trend of abusive passenger behaviour on planes.Briefing journalists this week, the International Air Transport Association (IATA) said it aims to use a conference in Montreal next March to seek agreement on the rights of crews and captains to do whatever is necessary to subdue offenders."Unruly passenger behaviour...is on the increase," Tim Colehan of the Geneva-based grouping told reporters. " It is a problem which our crews and other travellers face every day."He cited as typical a woman passenger who fought cabin crew after throwing liquor at them, and then shouted abuse at stewards and fellow passengers throughout an overnight flight from Europe to Thailand.Since 2007, when it began recording data, well over 15 000 incidents have been reported to IATA, Colehan said. "But there are almost certainly many more which we never hear about."The problem for the airlines and the crews, said Colehan, is that international law has not caught up with the new world of global air travel.Often offenders, like the violent woman passenger on the Bangkok flight, go scot free because police in countries where planes land say they have no jurisdiction. Lack of ClarityWorse, IATA says, the lack of clarity in the current 1963 Tokyo Convention that governs such cases leaves cabin crew and pilots uncertain on how to respond."There is always the fear that they could be sued for assault if they restrain a violent passenger," Colehan said.Other incidents in the skies this year include a violent attack on a stewardess in China, an American viewing pornography on his computer, and a South African couple having First Class sex, according to credible media reports.A Russian woman on a flight from Los Angeles to London drank liquid soap when refused alcohol, and tried to bite a steward. On another plane a man seized wine from a trolley and locked himself in the toilet to drink it.Several years ago, IATA told its 240-odd members - which include almost all the world's scheduled carriers - that they should back their crews and try to ensure that badly behaved passengers are taken to court.But the absence of well defined legislation means that this often leads nowhere. The Tokyo convention was originally drawn up to deal with hijacks.IATA wants governments to agree at the March conference, convened by the International Civil Aviation Organization, on a new convention that will spell out the right of an airliner's captain to do what he feels necessary to control misbehaving passengers.But the airlines are not sure of the outcome. "We are confident there will be a new convention, but - with so many governments having to agree - we have to wait to see how it turns out," Colehan said.