On June 21, 2001, at 1405 eastern daylight time, an amateur-built Masko Mustang MII, N24898, piloted by a commercial pilot, was destroyed when it impacted terrain following a loss of control while maneuvering in the traffic pattern at the Ann Arbor Municipal Airport (ARB), Ann Arbor, Michigan. The aircraft had just completed a touch and go and was turning from the upwind to the crosswind leg of the traffic pattern for runway 06 (3,500 feet by 75 feet, concrete). The local flight was being operated under the provisions of 14 CFR Part 91 and was not on a flight plan. Visual meteorological conditions prevailed at the time of the accident. The pilot and the pilot rated passenger received fatal injuries. The flight originated from ARB at 1353. Witnesses to the accident saw the airplane make a steep right turn prior to spiraling to the ground. A postaccident examination of the airplane revealed no anomalies that could be associated with a pre-impact condition. The pilot held commercial and certified flight instructor certificates with airplane single engine land and instrument airplane ratings. The pilot also held a ground instructor certificate with advanced and instrument ratings. According to Federal Aviation Administration records, the pilot reported having 398 hours of flight time as of March 15, 2001. The pilot's logbook was not recovered. The pilot rated passenger held a commercial pilot certificate with airplane single engine land and instrument airplane ratings. He held a certified flight instructor certificate with an airplane single engine land rating. The pilot rated passenger also held a ground instructor certificate with an advanced rating. According to Federal Aviation Administration records, the pilot rated passenger reported having 307 hours of flight time as of May 10, 2001. The pilot rated passenger's logbook was not recovered. Toxicology tests performed on the pilot and pilot rated passenger were negative for all tests performed. Autopsies were performed on the pilot and pilot rated passenger by Washtenaw County on June 22, 2001. It was reported that the airplane was purchased on June 16, 2001. The pilot was the flight instructor of the new owner. The owner was not aboard the airplane when the accident occurred.