Record-breaking cold has hit the Midwest, and more than 1,500 flights into and out of Chicago's O'Hare International Airport today have been cancelled.
The National Weather Service is warning of "bitterly cold" conditions, with highs from -9 to -13 degrees, and wind gusts up to 40 mph.
Even though planes are no strangers to strong wind and freezing temperatures when they fly at 30,000 feet up, ice and snow on the runways make takeoffs and landings more dangerous.
According to FlightAware.com, over 60% of those scheduled have been cancelled. More than 300 flights scheduled for Tuesday have already been cancelled as well.
Here's how the airport looked Monday morning:
According to Twitter user Sarah Mackey, it's so cold in the airport people can see their breath:
Yes, you can see your breath inside O'Hare airport... That's a new kind of cold! #polarvortex
- Sarah Mackey (@sarahwmackey) January 6, 2014
Not surprisingly, that's created some major lines at the airport. Here's a photo from CNBC's Phil LeBeau:
Pic of the day: Thousands delayed, cancelled. waiting in customer service line at O'Hare. pic.twitter.com/f8X1UGEdDc
- Phil LeBeau (@Lebeaucarnews) January 6, 2014
New York's JFK Airport was shut down Sunday morning after a Delta plane skinned off a runway, into the snow. No injuries were reported.