On March 13, 2006, about 2215 eastern standard time, a Saab-Scania AB (Saab) 340B, N421XJ, operated by Mesaba Airlines, was substantially damaged prior to departure from Alpena County Regional Airport (APN), Alpena, Michigan. The domestic air carrier flight was operating under 14 CFR Part 121 on an instrument flight rules (IFR) flight plan. Visual meteorological conditions prevailed at the time. The 11 passengers and 3 crewmembers were not injured. No ground personnel were injured. The scheduled passenger flight was preparing to depart APN, with an intended destination of Chippewa County International Airport (CIU), Sault Ste. Marie, Michigan. The operator reported that after the airplane's engines had been started, it was discovered that a baby stroller for an APN passenger had not been off-loaded. The station agents notified the captain, who shut down the left engine. An agent accessed the cargo compartment, located at the left, rear portion of the airplane. However, while he was exiting the compartment, the station agent lost his balance and dropped the stroller onto the ramp. The stroller landed on its wheels and was blown under the fuselage by the wind and into the right main landing gear. The stroller was subsequently blown forward into the right propeller arc, where the operating propeller struck it. Fragments from the stroller impacted the airplane's fuselage, puncturing three holes and causing several dents in the pressurized fuselage. The operator reported surface winds at the time as from 240 degrees at 20 knots, gusting to 31 knots. The APN routine weather observation (METAR), taken at 2154, recorded winds from 240 degrees at 17 knots, gusting to 27 knots.