funny you mention concorde..... i drove past one in france last week.
why did they ever decommmission it???
It was deemed too expensive to keep flying without the modifications and I have read that BA did not want anyone else to fly it. Others will confirm, no doubt. 
Indeed, as it lacked passenger payload capacity v. costs, so each passenger had to pay a considerable premium for flying on Concorde.
That actually produced a small profit on Concorde flights for BA when full. However along came the Paris crash, then worse still 9/11! It decimated passenger numbers on Concorde in particular, and spelt the end to a great aircraft that could never catter for the mass passenger markets due to the running costs.
The passenger loadings needed to be double the number from the start, with of course full access to all major USA airports which it never secured. The "son of Concorde" as envisaged by the great man himself, Sir Barnes Wallace, would have been double the size and no doubt would have overcome the issues of noise produced by those wonderful Olympus engines!
But that is one of those points in history of "if, maybe, should of, if only"!

One day supersonic passenger transport will return
