Severe weather has forced airlines to cancel more than 4,000 flights at major airports in US cities, including Chicago and Dallas.

Heavy snowfall and thunderstorms across the US hampered operations at major airports over the weekend, reported CNBC.

More than 1,000 flights were reportedly cancelled at O’Hare International Airport in Chicago due to heavy snowfall.

Passengers who departed on 14 April were delayed by an average of 44 minutes, according to the Chicago Department of Aviation.

Flight tracking site Flightaware.com said that more than 38,500 flights have been delayed and around 4,500 cancelled since 13 April.

“More than 1,000 flights were reportedly cancelled at O’Hare International Airport in Chicago due to heavy snowfall.”

American Airlines reportedly cancelled more than 1,700 flights due to snowfall over the weekend.

Southwest Airlines has cancelled more than 400 flights since 13 April.

Snowplows and de-icers were also being used at O’Hare Airport to clear the snow.

The Chicago Department of Aviation reported that 166 flights were cancelled at Midway International Airport.

In March, Denver International Airport (DIA) in Colorado, US, was forced to cancel approximately 1,400 flights on 13 March as a blizzard hit the airport.

The airport shut down all six of its runways amid low visibility on the airfield, but the terminal and concourses remained open.

Several airlines recently cancelled more than 750 flights to and from Denver International Airport (DIA) due to a blizzard known as Winter Storm Wesley.