More than 800 flights at DIA canceled Thursday as winter storm slams Colorado

As a major winter storm sets into Colorado Thursday, more than 800 flights at Denver International Airport were canceled by 6:30 a.m., according to airline tracking site FlightAware.

The storm, which forecasters at the National Weather Service in Denver expected to last until Friday morning, could drop up to 18 inches in the Denver area. Snowfall rates will likely worsen throughout the day Thursday.

At DIA, 802 flights have been canceled, almost evenly spread between arrivals and departures. There are also 35 delayed flights.

Nearly half of the canceled flights, 316, are through Southwest Airlines. That accounts for 51% of their Denver traffic.

Regional airline SkyWest has canceled 199 flights, or 75% of their Denver traffic.

Frontier Airlines has canceled 91% of their Denver flights with 124 cancellations. United Airlines has canceled 78 flights, accounting for 12% of their Denver traffic.

Other airlines with significant cancellations include CommuteAir and Mesa Airlines, with 30 and 29 canceled flights, and Volaris and AeroMéxico have canceled all of their Denver flights.

American Airlines, Air Canada, Lufthansa, Alaska Airlines and British Airways all have several canceled flights as well.

Southwest and United airlines issued travel warnings ahead of the storm and are allowing some customers to rebook their flights.

United customers who purchased their tickets on or before Sunday and are set to travel Wednesday, Thursday or Friday can reschedule their trip through March 19 with no fee or fare difference.

Southwest customers can rebook or travel standby within two weeks of their original travel date without additional charges, according to the alert.