Jeanne Stone-Hunter of the Wyoming Civil Air Patrol says the Piper PA-32 aircraft was reported missing after it failed to land as scheduled Tuesday evening at Casper/Natrona County International Airport.
She says searchers are concentrating their efforts on the Laramie Mountains between Casper and Cheyenne.
An initial search of the area Monday night by a Civil Air Patrol plane detected no emergency signals.
Stone-Hunter says the search on Wednesday was going until nightfall and would resume Thursday morning.
She says the flight originated from Harrison County Airport in Marshall, Texas, and stopped in Dodge City, Kan., to refuel.