Fast, reliable, direct rail links from Heathrow could be built to replace short-haul flights to cities such as Paris, Brussels, Manchester and Leeds. This approach has been adoped successfully elsewhere in Europe, for example to replace flights between Paris CDG Airport and Brussels.
Heathrow could become more of a destination airport and less of a hub. In 2006, 35% of passengers at Heathrow were simply changing plane there. Indeed, around 20% of Heathrow's passengers were foreign tourists who never entered the UK. Reducing this percentage could free up significant capacity.
The existing cap on the annual number of flights at Heathrow could be maintained and the price of using Heathrow determined by the free market. Limiting and charging for capacity is now an accepted approach for roads and road building in the UK - the same principle could be applied to aviation.
The proposals assume it acceptable that aircraft noise and pollution can be at similar levels in 2030 as they are today. Would we now live happily with the traffic pollution levels of the 1980s?
Everywhere else, there is an expectation that noise and pollution will be reduced over time. This principle should apply to Heathrow as well: the public should gain from the benefits of improved technology as well as industry.
Overall, the economic case for Heathrow expansion is unproven.
The City has expanded and is very successful despite Heathrow's congested terminals, lack of direct public transport links, and slow and unreliable road access. Liberal regulation, the use of English and a tradition of international trading have much more to do with the success of the City than Heathrow Airport.
Indeed, Heathrow is primarily an airport for leisure, not business travel. In 2006, only 26% of passengers at Heathrow were business travellers terminating their journeys there.
It's certainly true that Heathrow has benefited West London's economy. But that doesn't mean expanding Heathrow will provide significant further benefits. Since unemployment is relatively low in West London, employment demand may well be met largely from outside the region. This could locally drive up the cost of goods, services and accommodation.
There is no sensitivity analysis for these factors in the economic case. The true cost of some of these factors - for example CO2 emissions - may be significantly higher. The economic case should include "what-if" analyses to explore these risks.
The aviation industry is zero-rated for VAT and does not pay tax on fuel. The annual value of this is around £9 Billion. While the aviation industry does collect £2 Billion a year of air passenger duty, this still leaves it receiving substantial preferential treatment.
In 2006, 60% more UK leisure passengers than foreign leisure passengers terminated their journey at Heathrow. Assuming that this imbalance remains with an expanded Heathrow, the consultation estimates it could increase the tourism balance of payments deficit by up to £3.4 Billion. However, this is explicitly excluded from the economic case.
Some of the key economic research on which the economic case is based was paid for largely by the aviation industry. For such an important development, a separate independent economic assessment is essential to ensure there is no bias in favour of interest groups. If they expect the public to have confidence in their case for expanding capacity at Heathrow, the Government needs to commission such an independent study.
The Government proposes to mitigate the effect of the increased carbon dioxide emissions from the third runway by trading them.
Why should the aviation industry, uniquely, be able to expect other industries to make its emissions reductions for it?
How could we then ask growing nations such as China to curb their much bigger potential for aviation growth and the associated greenhouse gases?
Local air quality in the area around Heathrow is affected mainly by nitrogen dioxide emissions from cars and other road vehicles. With Heathrow expansion, the number of road passengers is expected almost to double.
Nitrogen dioxide limits in the vicinity of the airport are currently over EC guidelines. The pollution modelling used in the consultation relies on optimistic assumptions. There is no certainty that air pollution limits could be met with an expanded Heathrow.
The noise targets set by the Department for Transport for the consultation have been invalidated by their own research.
In November 2007 they issued the report of a study on the effects of aircraft noise they had commissioned in 2001. This indicated that their choice of the 57 decibel line to define the threshold of noise nuisance was arbitrary, and that noise annoyance started at much lower levels and hence was spread over wider areas.
They have explicitly ignored these findings and instead are basing their noise criteria on a 22-year-old paper which was never peer-reviewed.
Busier skies and more complex arrival and departure patterns compound the risk that an accident will occur as a result of Heathrow expansion.
The proposals explore only the principles of how an expanded Heathrow would operate, yet the detail is key to safety and to the public perception of safety.
Producing a safety plan should be a priority.
The Government has left details of improving public transport access to the airport to the planning stage of any development.
Yet the current poor provision of direct public transport links to Heathrow contributes significantly to road traffic congestion resulting in delays, carbon dioxide emissions and local air pollution.