So guess what operators are always looking to be above that figure. It keeps the locals out of the frame better
The whole process is a mess, and it's not helped by those who've made a good living out of ATC/Airports who are very quick to turn round and sell their souls to the wind energy companies in order to undermine legitimate concerns surrounding the impact of turbines on an airports PSR.
In fairness to the energy companies though, at least the enquiry get's round NIMBY policies like 'no wind farms in Northumberland'.