The world's airline industry may have only one way to escape the surge of enthusiasm to punish its carbon dioxide emissions with taxes or even regulatory limits on air travel, and that's a global emissions trading arrangement that is probably years away from implementation.

Industry leaders feel carriers are faced with shouldering the unwelcome cost of such a plan to avoid suffering worse impositions devised by politicians who want to be seen doing something about global warming and find that airlines offer a suitably headline-grabbing target.

If aviation cannot come up with a workable system, "we need to be prepared for individual states to apply opportunistic taxes dressed up as green taxes," says Andrew Herdman, director general of the Assn. of Asia-Pacific Airlines (AAPA).

The cost of buying emissions permits might not be great--maybe only 3% of global airline revenue, even if carriers had to pay for all of their greenhouse pollution, which would be unlikely.

The alternative punitive taxes are already on the agenda, especially in Britain, and the risk is that more will follow while airlines wait for the International Civil Aviation Organization (ICAO) to come up with the emissions trading system now being lobbied for by industry leaders.

Paying other sectors for rights to pollute is hardly an attractive prospect for an industry that is barely profitable, but a conference in Hong Kong on Mar. 29-30 found no other solution likely to get aviation off the hook.

The airlines feel they don't need to be told to burn less fuel, and they point to the relentless 1-2% annual improvements in aircraft efficiency that the engine and airframe makers have been delivering for decades. Their problem lies in that virtue: because they have always made fuel economy a high priority, there's very little they can do to meet sudden calls for big improvements.

Meanwhile customers demand about 5% more air transport each year, so the industry's output of greenhouse gases is rising.

One political response could be to stop the growth or even force reductions in flying, a nightmare for airlines and their suppliers. The alternative pushed by the International Air Transport Assn. (IATA) and some airlines is to neutralize the environmental effects of traffic growth with the trading system, in which carriers would buy the rights to pollute from industries that could economize more easily and could therefore afford to sell.

Among other measures explored at Orient Aviation's Greener Skies conference: