On August 23, 2001, approximately 1800 central daylight time, a Piper PA-18-150 single-engine airplane, N91178, registered to and operated by the U.S. Border Patrol of Marfa, Texas, was destroyed upon impact with terrain following a loss of control while maneuvering near Van Horn, Texas. The instrument rated commercial pilot, sole occupant of the airplane, received minor injuries. Visual meteorological conditions prevailed and a company flight plan was filed for the 14 Code of Federal Regulations Part 91 Public Use flight. The aerial observation flight originated from Marfa, Texas, at 1530. In the enclosed NTSB From 6120.1/2, the 1,668-hour pilot reported that he was performing routine patrol duties over rolling terrain at an estimated altitude of about 500 feet above ground level. The pilot added that he "made a right turn and crossed a ridge when the bottom fell out." The pilot further stated that he applied full power and leveled the wings in order to recover; however, his actions were not sufficient to arrest the rate of descent and the airplane impacted the next ridge line. The FAA inspector, who traveled to the accident site, confirmed that the airplane was destroyed by impact forces. Examination of the 1981 model airplane, which at the time of the accident had accumulated a total of 8,889 hours, did not reveal any anomalies that could have prevented normal flight operations. Company records confirmed that the pilot had accumulated a total of 1,668 hours, of which 192 hours were in the same make and model of airplane. At the time of the accident, density altitude was calculated by the NTSB investigator-in-charge as 7,428 feet.