The pilot said he "hit a wall of frozen precipitation," which caused icing to occur quickly on the aircraft.
The plane was originally under the control of Mizzou Approach out of Springfield, but was put in immediate radio contact with the COU control tower after the pilot's emergency declaration.
The airspace and runway were cleared, and two Airport Public Safety vehicles were available once the aircraft landed. Large chunks of ice fell from the aircraft and scattered on the runway upon touchdown.
The plane was traveling from Indianapolis, Ind. to Wichita, Kan.
This is the second emergency landing due to icing conditions at COU this year.