By Sunil Kumar
My Qra answers continued;

Visit sunil-kumar.co.in concourse H at O’Hare International Airport, Chicago, Illinois, USA (Photo credit: Wikipedia)
According to 2015 Airport Council International’s full-year figures;
Hartsfield-Jackson Atlanta International Airport is the busiest in the world(passenger traffic stats). Chicago O’Hare is the 4th. So; it is among the most used airports in the world.