In 2007, the European Union (EU) created quite a stir by proposing a kind of "tax" on all flights that arrived or departed from any EU airport, arguing that this would help curb the growth in carbon emissions.

Airlines - the world over - were enraged and their objections to the proposed unilateral step raised hackles at the meeting of the International Civil Aviation Organisation (ICAO) held in September 2007.

The airline industry shouted back that their emissions were nothing when compared with the auto industry, and so there's no reason for them to be singled out.

The truth, however, is that total airline industry emissions have increased dramatically in the past decade as more flights have taken off due to the emergence of low cost air travel. ICAO predicts that airline emissions will rise to 3 per cent of total carbon emissions by 2050, if left unchecked.

I'm no expert at this, but anyone who has seen and digested the full meaning of Al Gore's "An Inconvenient Truth" will quickly see the sense in reducing emissions on a truly urgent basis.

The Indian government too has now woken up to the potential dangers of airline emissions and has recently asked the Bureau of Energy Efficiency (the ministry of power) to conduct a baseline survey on the extent of emissions by Indian carriers and what can be done to reduce them over time.

Airbus and Boeing - the two largest aircraft manufacturers - have also started making all the right noises and claim that they are leaving no stone unturned in searching for alternative, cleaner fuels and improving the energy efficiency of their aircraft. Both are looking for funding support from their governments to do this.

In a world that's increasingly concerned about - and is, in fact, witnessing � the impact of global climate change, I read with some disbelief that Mukesh Ambani, chairman of Reliance Industries [Get Quote], had gifted his wife with an A319 on her 44^th birthday last November.

The aircraft, which can normally accommodate 124 passengers in a typical two-class configuration and is used by several low-fare airlines around the world to ferry passengers, will be exclusively at the service of Mrs Ambani and, I presume, whoever accompanies her. According to media reports, the luxury jet, which cost $40-60 million, has been custom-made and will have a master bedroom, a

bathroom with a range of showers, a bar with mood lighting, a cabin with game consoles, music systems, satellite television and wireless communication.

Within a week of Mukesh Ambani's present, Saudi Prince HRH Prince Alwaleed bin Talal bin Abdulaziz Alsaud, who is the only private owner of a B747-400, became the first to buy an A380 Flying Palace, becoming the first customer for the VIP version of the new double-deck airliner.

The aircraft, which in an all-economy configuration can seat over 800 passengers, costs $300 million in the ordinary passenger edition.

These are not the only people with indulgences. Business jets have been a growth business for some time, and several Indian businessmen have been acquiring them in recent years. Vijay Mallya was among the first to acquire a four-engine personal jet, and now flies a full passenger jet as his personal carrier.

Mukesh Ambani is in the same league and has bought himself a Boeing Business Jet 2 (BBJ2), priced at $73 million, which can take up to 78 passengers. The BBJ2 is the tenth aircraft in his fleet, making it larger than the fleet operated by the Mumbai-headquartered low-cost airline Go Air and equivalent to several small carriers in south-east Asia and south Asia.

Normally, one would accept the argument that those who earn their money have every right to spend it any way they wish - Mallya, for instance, has been buying F1 teams, South African game parks and what have you.

As billionaires have proliferated, corporate jets have grown in size to become more comfortable for their owners, many of whom may well spend more time in the air than on the ground. But I can't help feeling that in some of these cases, we are partly paying for someone else's excesses.

One expects a profligate lifestyle from a Saudi prince. But should our homegrown maharajahs be so unmindful of their impact on the environment, and the size of their personal carbon footprint?

There is another point here. If Airbus and Boeing are as keen to be "green" as they claim, they and all the other manufacturers of business jets need to be asked - perhaps through ICAO's persuasion or some other diktat - to keep their corporate jets at a certain globally acceptable size.

Taking it a step further, the two manufacturers can be asked to walk their talk by refusing sales of large wide bodied aircraft to individuals - unless the usage is justified - instead of gleefully pursuing and then publicising them.