It has been said that Best Practice (BP) is to apply better practices of quality in customer service. In some way that is correct, since operating by meeting minimum regulatory requirement only is not intended to produce satisfactory customer service.
On that day when an enterprise was issued an aviation operating certificate, they were regulatory compliant. This was a static mode, where there had been no movements of aircraft or operation of the airport. Maintaining this status quo of regulatory compliance as it was at the issuance of an operation certificate is neither practical nor the intent of the certificate.
Best Practice is to establish customer friendly processes.
An enterprise; when operating airplanes or airports must establish processes that is conforming to regulatory compliance. Establishing these operational processes is to go beyond what regulation requires. This is Best Practice; It's to establish processes above and beyond what the regulation requires and to maintain operational processes which are conforming to regulatory compliance.
Is an airline required by regulations to employ baggage handlers and ground crews? However, as ground crews tasks are related to aircraft operations they must be trained in operational procedures, and be qualified to advise the Captain. A "thumbs up" when nose wheel is disconnected doesn't just say "have a safe trip".
When going "where birds don't fly" processes are conforming to regulatory requirements. Flooded airport is regulatory compliant by NOTAM closed.
An airport may be regulatory compliant by issuing a NOTAM of airport closed and an airline may be regulatory compliant by grounding airplanes. However, by doing that, there is lack of customer service.
Best Practice (BP) is what an Enterprise does to ensure operational processes conform to regulatory compliance by developing and maintaining processes of regulatory requirements.