Southwest to Nashville, Tennessee out of Denver, Colorado is getting de-iced.

In aviation, ground deicing of aircraft is the process of removing surface frost, ice or frozen contaminants on aircraft surfaces before an aircraft takes off. This prevents even a small amount of surface frost or ice on aircraft surfaces from severely impacting flight performance. Frozen contaminants on surfaces can also break off in flight, damaging engines or control surfaces. All airports in climates conducive to ground icing will have some kind of ground deicing systems in place. Ultimately it is the pilot-in-command's responsibility to ensure that all necessary deicing processes are carried out before departure. Aircraft are often equipped with ice protection systems and/or icephobic surface coatings to control in-flight atmospheric icing, however those are not considered substitutes for adequate ground based deicing.