are used by one or more
to concentrate passenger traffic and flight operations at a given
. They serve as transfer (or stop-over) points to get passengers to their final destination.
It is part of the
. An airline operates flights from several non-hub (spoke) cities to the hub airport, and passengers traveling between spoke cities need to connect through the hub. This paradigm creates
economies of scale
that allow an airline to serve (via an intermediate connection) city-pairs that could otherwise not be economically served on a
basis. This system contrasts with the
, in which there are no hubs and nonstop flights are instead offered between spoke cities. Hub airports also serve origin and destination (O&D) traffic.