ff/SC
I disagree. Sywell is, primarilly, an airfield. It's primary customers are pilots. It has a duty to provide a service, which its customers pay for - that service is the provision of a useable airfield during its published operating hours.
McDonalds are primarilly a fast-food outlet. They also run childrens' birthday parties, but they ensure that their fast-food customers are still able to buy food when parties are taking place. Tescos are primarilly a supermarket. They also sell clothes and electrical goods, but that doesn't prevent their customers from doing their weekly grocery shopping while clothes are on sale in a different part of their stores.
If Sywell aren't able to operate a conference centre without jeapordising the operation of the airfield, then they shouldn't, IMHO, operate a conference centre at all. Or, alternatively, they should re-market themselves as a conference centre which happens to have a runway on-site.
I'm not sure that comparisons with North Weald are valid, because - correct me if I'm wrong - I don't believe NW charge a landing fee. Therefore, the pilots who fly into NW are "users" of the airfield, but not "customers". (I have, from time to time, been known to offer IT training or consultancy to family and friends free of charge. My level of professional responsibility to family and friends is far lower than the level of responsibility I have towards my employer, or anyone else who pays for my services.)
FFF
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