Priority Pass is a product that potentially provides consumers with access to airport lounges that Priority Pass has contracted with.
The word "Priority" is somewhat of a misnomer.
What has been prioritized is alliteration over accuracy.
Priority Pass allows airport lounges to bring in incremental revenue by providing access to Priority Pass members if space is available during a given time.
Think of the relationship betweeen Priority Pass and airport lounge operators as being the opposite of that between Burger King, McDonald's, Wendy's, and their franchisees.
Once constructed and in operation, a fast food franchise must strictly comply with the chain's rules.
In contrast, airport lounges are often constructed as a perk for an airline's highest valued passengers.
A collection of airport lounges or an individual airport lounge might choose to affiliate with Priority Pass but even then Priority Pass does not have the ability to dictate the terms of the relationship.
Out in suburbia, Burger King seems to be able to find space for a franchise across from, if not outright adjacent, to a great number of McDonald's franchisees.
Airport lounge space is a less elastic resource.
Other than discriminating against any legally protected classes, airport lounge operators have discretion over who to admit.