suprised you've been sold on the whole Heathrow must expand or we die spin.
I was actually convinced by a good friend who works in the industry. Increasing the capacity is one argument for the new runway. He suggested that it needs a 3rd runway just to be able to work its current capacity in a much more effient manner i.e. reducing delays and stacking etc. I understand Heathrow is poor when it comes to delays.