What is defined as an "offline station"?

An "offline station" refers specifically to a city that is not serviced by the airline on a scheduled basis. This means that there are no regular flights operating to or from this location, making it unavailable for routine travel on that airline. The term is used to distinguish between cities that have established routes and those that do not have any scheduled flights, regardless of their geographical location or potential demand for air travel.

The other choices highlight different types of cities in relation to airline services but do not accurately describe what an offline station is. A city serviced frequently by the airline indicates an active route, while a city with limited airline services suggests that there may be some connections but not robust or consistent ones. A city primarily used as a connecting hub denotes a location with scheduled operations aimed at facilitating connections, which is contrary to the nature of an offline station. Thus, understanding the definition of an offline station helps clarify the terminology used in the airline industry and assists in better grasping the structure of airline routes and services.