  The optimal solution of an inter-city passenger transport network has been
studied using Zipf's law for the city populations and the Gravity law
describing the fluxes of inter-city passenger traffic. Assuming a fixed value
for the cost of transport per person per kilometer we observe that while the
total traffic cost decreases, the total wiring cost increases with the density
of links. As a result the total cost to maintain the traffic distribution is
optimal at a certain link density which vanishes on increasing the network
size. At a finite link density the network is scale-free. Using this model the
air-route network of India has been generated and an one-to-one comparison of
the nodal degree values with the real network has been made.
