Elsewhere on this forum is an excerpt from the 'Telegraph' which explains how expansion of STN would be at the expense of LGW and LHR users.
Since the current development was started at STN around ten years ago, it has received huge subsidies from elsewhere in BAA. In order to reduce the burden of its white elephant, BAA has offered 'sweetheart' deals to numerous airlines. The effect has been to attract passengers to an airport they would rather not fly from.
A quick look at a decent map of England (supported by more detailed analysis) shows that the most conveniently located South-East airports for the population they serve are (in order): Heathrow, Luton, Gatwick, Stansted. (this excludes LCY because of its operational limitations).
It is no surprise that most of the development has gone into the three BAA owned airports, whilst the independent one has been discriminated against by Governments of all persuasions.
I strongly maintain that 14 million people don't want to fly from Stansted, and if the £500 million spent on STN had been spent at Luton, all users would be more satisfied. Airlines because there would have been more equal competition for their business, passengers because LTN is more convenient, and environmentalists because surface access journeys (far more intrusive and polluting than aircraft) would have been shorter and more heavily rail-based.
BAA are still offering cross-subsidised deals to new airlines at STN, and will continue to do so until stopped. The only beneficiaries of such deals are BAA shareholders, who are minimising their losses at STN.
I repeat my call, based on a solid case of facts, for BAA to be investigated and/or broken up.