A reality from the ATC perspective is that even if there was not a single increase in flights through Heathrow, the 3rd runway was needed 15 years ago. There is, in my view, unacceptable pressure on ATC to deliver minimum spacing all the time and in all conditions. Being scheduled at 98% of absolute capacity means there is no slack available in an industry that relies on human beings. We WILL make mistakes, therefore minimum approach spacing should never become maximum too.
The government's policy of "...best use of existing runways." has been interpreted to mean maximum use. I believe that is a fundamental flaw in strategy and one that leaves the whole system exposed.
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