Skipness One Echo - LHR has the critical saturation that allows for such high yields. Not many other airports have that, not even AMS or MAD come close. CDG and FRA can compete but to a much lesser extent. However, you seem to be speaking from an airlines profitability perspective rather than the arguement about what is good for the economic competitiveness of the economy, which is what the 3rd runway arguement is about. London is one of the largest business hubs in the world, airlines will continue to fly here, no other city of its size and stature can claim to have so many airports serving it. LGW can quite easily become a business airport for London playing the niche card as it already has done as the UK's new gateway to Asia.