What feature characterizes a pier terminal?

A pier terminal is characterized primarily by its design in which concourses extend out from a central terminal building, resembling a pier. This layout allows for a more efficient flow of passengers, as gates are organized in linear fashion leading directly from the main terminal. Such a structure can facilitate easier access to aircraft while minimizing the distance passengers need to travel between the terminal and the gates.

The other options may relate to different terminal structures or airport designs. For example, having all functions in one building is typical of a terminal with a more compact layout but does not define a pier terminal specifically. Isolated parking facilities could be applicable to various terminal configurations and do not denote the pier concept. Lastly, a high percentage of transfer passengers is generally a feature of hub-and-spoke airport designs rather than a characteristic associated uniquely with pier terminals.

Thus, the characteristic feature of concourses extending from a main terminal distinctly identifies a pier terminal within airport architecture.