Max Wurr, Stanmore, UK. The largest (heaviest) flying bird today is the Kori Bustard (Ardeotis kori) of Africa, males weigh about 18kg, females about half that. The largest bird ever to fly were the Teratorns (a type of Condor), the largest of which, Argentavis magnificens, had a wingspan of 3 metres, and weighed 120kg.