On October 27, 2000, about 1534 eastern daylight time, a Waco UPF-7, N32049, registered to and operated by Island Aero Tours, turned over inverted when control was lost during landing roll at Key West International Airport, Key West, Florida, while on a Title 14 CFR Part 91 sightseeing flight. Visual meteorological conditions prevailed at the time and no flight plan was filed. The aircraft received substantial damage and the commercial-rated pilot was not injured. The two passengers reported receiving minor injuries. The flight originated from Key West, the same day, about 1500. The pilot stated that during landing rollout on runway 9, the aircraft was rolling straight on the center when it turned hard to the left. He applied full right rudder and full left aileron, but the aircraft continued turning. He then applied full right brake, but the aircraft continued to turn to the left. The left main wheel then lifted off the runway and the aircraft started going straight. When the left wheel touched back down on the runway, the aircraft nosed down and the propeller and engine contacted the runway. The aircraft then nosed over and came to rest inverted on the runway. He stated he did not use any left brake during the landing and that he believes the passenger in the front seat applied the left brake during the landing roll. The aircraft operator stated that the main landing gear wheels could be turned freely after the accident and that there was no evidence of failure or malfunction of the main landing gear brakes. The runway had faint tire marks from the left main tire and heavier tire marks from the right main landing gear. The pilot had made eight or nine prior flights that day in similar wind conditions. The two passengers were seated in the front cockpit and each had access to a brake pedal. The passengers were briefed by the office secretary and the pilot before the flight to avoid the brake pedals. The passenger seated in the left front seat stated he and his wife were in the front. His wife was on the right. They were briefed about the controls in the front cockpit and told not to touch them. This included the pedals on the floor. At no time during the flight did he touch the flight controls or pedals on the floor and his wife could not reach the pedals. When they landed, the aircraft went to the right first and then back to the left. It then nosed over and came to rest upside down.