I don’t believe DSA is a vital part of the national infrastructure, in the case of South Yorkshire there is MAN, LBA, EMA and HUY within relatively easy reach.
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MAN,LBA,HUY,EMA are all on extremes of the great County – Given no one will build a New airport in Yorkshire, Hypothetically speaking isn’t DSA the only viable semi central location, with Motorway & Rail access that has any potential for growth to say STN levels of traffic? Surely that would make it a vital part of National Infrastructure to the UK’s largest Counties of Yorkshire & Lincolnshire.