On January 15, 1995, at 1834 central standard time, a Piper PA- 28-181, N39955, registered to Thunderbird Trans LTD, was destroyed when it stuck trees while on final approach to land at Capitol Airport, Brookfield, Wisconsin. The flight instructor, private pilot, and one passenger reported serious injuries. The local night 14 CFR Part 91 instructional flight originated at 1745 and operated in visual meteorological conditions without flight plan. After returning from the local practice area on the instructional flight, the private pilot proceeded to perform three takeoffs and landings at Capitol Airport. The flight instructor accepted the private pilot's invitation to do the fourth approach and landing by taking full control of the airplane. The instructor stated all appeared normal including centerline tracking during the final approach. While the airplane was on short final, the left wing struck a tree and the instructor immediately applied full power. The left wing impacted a second tree and was separated from the airplane. The airplane impacted the ground in an inverted position. No preimpact mechanical or other anomalies were reported by either the instructor or the private pilot.