Air travel is one of the great liberations of modern technology; people should travel to the four corners of the earth, but they must pay for the environmental damage they cause.

Now is a good time to fly, despite – or, rather, because of – all the bad news. Paradoxically, our awareness of the terrorist threat makes air travel safer than ever. And, in a longer-term view, air travel has never been so cheap, and may never be so cheap again. It is certainly desirable that air travel should become much more expensive in the next few years.

This is not merely in order to pay for the "sky marshals" proposed by the Government's review of airline safety. (Whatever the pros and cons of guns on board, enhanced security will cost money.) Nor for higher airline margins in the wake of United Airlines' teetering on the edge of bankruptcy in the US.

Above all, it is about ensuring that passengers pay the full environmental cost of air travel. The Royal Commission on Environmental Pollution reported last week on the effect on climate change of the rapid growth in aircraft emissions. This is a long-term challenge to the world's leaders, who have only just begun to notice the blip on the radar. Although noise pollution and the planning of new runways are important, and have dominated the debate in this country, the question of global warming is the most serious in the long run.

Unfortunately, the members of the Royal Commission tend towards the typical green activists' mistakes. They urge the Government to stop building any more airports or expanding any existing ones. That is a crude and counter-productive way of engineering higher ticket prices. It was not helped by snobbish comments about the ease with which people fly to Venice for the weekend now instead of, as in the old days, for two weeks.

The first problem is that aviation fuel is too cheap. It should be taxed as heavily as fuel for other forms of transport. The second problem is that landing slots at airports are too cheap, and allocated by governments to favour national carriers. They are a scarce resource which should be sold to the highest, most efficient, bidder.

Air travel is one of the great liberations of modern technology. People should travel to the four corners of the earth – for the weekend if they want. But they must pay for the environmental damage they cause, including the local costs of building new airports.