On May 20, 1998, approximately 0915 mountain daylight time, an Air Tractor AT-401, N1009T, collided with a power transmission line during an aerial application flight about two miles northwest of Idaho Falls, Idaho. The commercial pilot, who was the sole occupant, received minor injuries, and the aircraft, which was owned and operated by the pilot, sustained substantial damage. The 14 CFR Part 137 flight, which originated at an agricultural airstrip near Osgood, Idaho, was being operated in visual meteorological conditions. According to the pilot, who had been maneuvering near the power line while applying chemicals to a field, he was just rolling wings-level and descending for another pass when his left wing contacted the top wire of a power line located just beyond the boundary of the field he was spraying. He said that he saw the line and thought he had clearance, but the aircraft's wing caught the wire near its tip. He reported that after colliding with the power line, the aircraft struck the ground in a "cart-wheeling" motion. He further stated that he was accustomed to flying the AT-300, but that he had recently purchased the AT-401, and that this was his first application flight using the new aircraft. It was his opinion that the different size and sight-picture of the 401 had caused him to think he had more clearance from the wire than he actually had.