URUMQI, Dec. 12 (Xinhua) -- Heavy fog has enveloped Urumqi, capital of northwest China's Uygur Autonomous Region, over the past three days, affecting over 900 flights at the city's airport.

The foggy weather has lasted more than 60 hours by Thursday noon, with no flights taking off or landing in nearly 40 hours, according to the operator of the Urumqi Diwopu International Airport.

The massive air traffic disruption has affected more than 100,000 passengers, it said.

Local railway authorities have helped carry more than 2,500 air passengers to and from the Turpan airport, an alternate airport for the Urumqi Diwopu International Airport in extreme weather.

The heavy fog is forecast to last till Saturday, according to the Xinjiang meteorological center.