On May 7, 1993, about 1140 central daylight time, a passenger attempting to board Air Wisconsin flight 5270 at Green Bay, Wisconsin, fell on the airplane's integral airstair door and fractured her left knee cap. The airplane, N852AW, a British Aerospace ATP, was not damaged. The destination of the 14 CFR Part 121 passenger flight was Chicago, Illinois. Visual meteorological conditions existed at Green Bay at the time of the accident.

The 73 year-old passenger reported she had made the first step, but her foot caught on the second step before she had grasped the hand rail. She said she then lost her balance and fell.

The passenger was treated by paramedics and transported to a local hospital.