On June 7, 1997, about 0930 central daylight time, a Piper PA-25, N6339Z, received substantial damage on impact with a FM radio tower. The commercial pilot sustained fatal injuries. The airplane impacted a guy wire approximately 30' below the top of the 971' tall tower located 9 miles southeast of Sullivan, Missouri. The 14 CFR Part 91 flight departed Saint Charles, Missouri, at 0830 for re-positioning to an undetermined location. Witnesses at the accident site stated at the time of the accident, visibility at the surface, was restricted to one-quarter mile in fog. Witnesses stated that the pilot who was the operator of "Cloud 9 Soaring" which operated out of the Sullivan Airport, rented the airplane with the intention of towing a banner. A flight instructor at Washington, Missouri, reported on the morning of June 8, 1997, that he found a banner used by Cloud 9 soaring set up at the Washington Municipal Airport. Washington Municipal Airport is located 28 miles southwest of Saint Charles. The Sullivan Airport is located 49 miles southwest of Saint Charles. The tower and accident site is located 52 miles southwest of Saint Charles, and 10 miles southeast of the Sullivan Airport. The operator where the pilot rented the airplane said that the airplane was rented with the fuel tanks full. A witness who was at the Sullivan Airport on June 7, 1997, stated that at 0930 there was a 200 foot overcast. A witness across the road from the tower said that about 0900 to 1000 he heard a low flying airplane, but that he could not see the airplane because of restricted visibility due to fog. He further stated that he "could hardly see the power lines which is about 100 yards from where I was." He said he did not see or hear the impact. Visual Flight Rules (VFR) charts found in the wreckage of the airplane did not depict the tower, its height, nor its location. The airplane was not equipped and was not certified for flight by reference to instruments. An inspection of the airplane wreckage failed to reveal any preexisting mechanical anomalies. There were marks on various parts of the airplane consistent with contact with the cables of the tower. Debris from the airplane remained attached to one of the top cables approximately 100 feet from the center of the tower. The propeller blades had leading edge damage and there was chordwise scratching on the camber side of the propeller blades. The toxicology report indicated quantities of Fluoxetine and Norfluoxetine in the pilot's post mortem specimens of blood and liver fluid. The drugs detected are a form of the prescription drug Prozac. Frequently Prozac is prescribed as an antidepressant, and also used in the treatment of obsessive-compulsive disorder. The Federal Aviation Administration does not permit an aviation medical examiner to issue a medical certificate to a pilot on mood-altering medications such as Prozac. Possible effects of the drug on the pilot's performance is unknown.