LONDON, England (CNN) -- The worst snowstorm to hit Britain in 18 years forced the cancellation of more than 650 flights at London's Heathrow airport Monday and shut down the city's bus network, partially paralyzing the British capital. A group of men push a giant snowball across Kensington Gardens, west London Monday. Heathrow, one of the busiest transport hubs in the world, closed both its runways for more than two hours Monday morning and operated with just one for the rest of the morning, according to BAA, the company which runs it. London City airport is also closed, while the British capital's other two airports, Stansted and Gatwick, were operating with severe delays, BAA said.
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UK business spokesman: Disruptions would likely cost $1.7 billion
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Meteorologists said snow is worst in southeastern England in 18 years
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Major international airports including Heathrow, Gatwick badly affected
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UK weather service issues severe weather warnings for Monday, Tuesday
"Bus services were suspended throughout London last night on the grounds of passenger safety due to the unsafe road conditions resulting in a large number of traffic incidents across @placeholder," the agency said in a statement Monday morning.