(NBC News) — More than 1,200 flights within, to and out of the United States have been canceled as of Thursday morning, according to FlightAware.com. Another 1,218 flights within, to and out of the U.S. are delayed.

Chicago O’Hare International Airport said it pre-emptively canceled nearly 400 flights. Meanwhile, Kansas City International Airport urged travelers to check their airline carriers’ websites for the latest information.

“We expect airline delays and cancellations in advance of and during the approaching snow storm, some even tonight,” it said in a tweet. “Many airlines are waiving change fees.”

Read the full story on NBCNews.com.