Heathrow is also Europe 's busiest airport for passenger traffic , and handles more international passenger traffic than any other airport in the world . Heathrow is owned and operated by BAA Limited , which also owns\/operates six other UK airports and is itself owned by an international consortium led by the Spanish Ferrovial Group . BAA claims that Heathrow is the `` world 's busiest international airport '' , but in 2010 it was only the world 's fourth-busiest by total passenger traffic , after Atlanta , Beijing and Chicago O'Hare which are also international airports .