Several of the UK's airports are discussing plans to expand. While Friends of the Earth opposes any expansion, the British Airports Authority, which runs seven British airports, says it will expand if there is enough demand. Both groups tell us why.
MARK MANN, BRITISH AIRPORTS AUTHORITY
The government is driving the expansion of airports. They, along with other groups, have made all of the arguments for increased revenue and have pointed out that more air passengers is good for the economy and generates revenue for businesses through tourism.
BAA says passenger numbers continue to grow
From our point of view, airports are completely capacity constrained. At peak times there are no spare slots at Heathrow or Stansted. They are full to capacity. And Gatwick is returning to its pre-9/11 levels.
We can accommodate 3% growth a year in terms of passenger numbers, but we are anticipating demand of 3.9%.
At the moment we are working to get the maximum possible use out of our airports. The government has asked us to do this before we expand, and we are spending £500m on making sure it happens.
By the time expansion comes on stream - Stansted is expected to get a second runway by 2013 at the earliest - any slack in the system will have been taken up.
But expansion is not a forgone conclusion. Stansted is the first airport earmarked, but even then we still have to put forward our formal planning proposals to the local authorities.
This is not expansion at all costs - this is not the airports going out there to carpet the countryside in concrete. Any expansion of our airports will be done on a sustainable basis, with approval from the relevant authorities, and only where expansion is needed.
RICHARD DYER, FRIENDS OF THE EARTH
There is absolutely no justification for building more runways. We could be flying a lot more aircraft from the ones we've already got.
Currently there are about 200 million passengers flying every year. With our existing capacity, we could still handle 300 million passengers.
Green groups say expansion will damage the environment
The government is expanding airports because they predict that the numbers of air passengers will continue to rise.
We have proved using the government's own projections that if you taxed fuel and added VAT - essentially stopped subsidising the aviation industry - the numbers of passengers would stay the same, or would fall.
The government also needs to work on the train network to give a better alternative to air travel. The trains need to be better at linking across Europe and need to be cheaper, faster and easier to understand.
Having said that, a recent survey of London's air routes showed six out of the top 10 destinations from the capital can be reached by high-speed rail link. They include Paris, Brussels, Frankfurt, Amsterdam, Edinburgh and Glasgow.
We also do not accept the economic benefits from having more air passengers. Most flights from regional airports go to holiday destinations like southern Spain. British people spend far more on tourism abroad than foreign holidaymakers do in Britain.