Date: 201508
Local time of day: 0601-1200
Location: ORD.Airport, IL
Weather elements / visibility: Thunderstorm
Aircraft: B737-900
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Parked
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Anomaly: Ground Event / Encounter Object
Detector: Person Flight Crew
When detected: Aircraft In Service At Gate
Result: Aircraft Aircraft Damaged; General Flight Cancelled / Delayed; General Maintenance Action
Contributing factors: Equipment / Tooling; Human Factors; Weather
Primary problem: Weather

Narrative: Flight Attendants were on board; Captain had just left flight planning outbound to gate for restroom. FO in terminal on food run for flight attendants.Went from nice day to zero visibility with heavy hail; lightning and high winds in a matter of seconds. Lasted about 10 minutes. Captain saw this; ran down terminal and down to the airplane.During this time; a baggage cart hit the airplane just aft of rear left wing root fairing. When Captain got down to airplane; flight attendants advised that something had hit airplane and they were preparing to leave (they thought it was hail or some other storm related damage).Waited about 2-3 minutes and freak storm was gone. Went down to ramp; saw that one corner of baggage cart had contacted the fuselage of the airplane about 5 feet off the ground just aft of rear left wing root fairing. It actually contacted where the fairing connects to the fuselage. Fuselage was bent inward from the impact damage an inch or two.Ramp agents were there. Asked them not to move anything; and to chock all three landing gears of airplane as well as all wheels of the baggage cart and not to move anything until advised.Contacted Dispatch to advise; asked to be transferred to Maintenance Control. Spoke with them; took pictures and emailed. Went to the gate agents at the counter and told them what had happened. Made an announcement to the passengers to assist gate agents. Called Duty Manager to advise of situation. Advised flight attendants and First Officer what was going on.Went back down to ramp; ramp management was there; and they weren't sure how the baggage cart impacted the airplane; but they took responsibility for it. My *assumption* is that the high winds blew the baggage cart from where it was standing to the airplane. I don't think it was driven there. Reports from ramp personnel indicated that the baggage cart actually travelled through several gate areas before impacting us (adjacent gate; at least; was vacant at time of incident.Further discussed situation with Ramp Tower and was told several airplanes were damaged during the storm. Violent storm caused the baggage cart to become unsecured and impact the airplane; or caused unsecured baggage cart to impact the airplane.




Synopsis: A B737 Captain experiences a very strong thunderstorm while in the terminal between flights. After arriving at the aircraft it is discovered that a baggage cart; belonging to another carrier; has been blown across the ramp causing damage to the aircraft fuselage.