What happened
The flight experienced delays of over 30 minutes following a period where a mechanic advised the captain that a serviceable part required replacement from another aircraft. Shortly thereafter, maintenance control decided against the part swap, and the mechanic informed the captain that the aircraft was "all closed up and ready to go." This communication led to a misunderstanding; the captain interpreted this as all aircraft doors being secured, whereas the mechanic intended to communicate that only maintenance access doors were locked.
At the time of the pushback, the L2 door remained open, and the jet bridge was still attached to the aircraft. Additionally, a gate agent remained onboard the aircraft to manage an oversold passenger situation, unbeknownst to the flight crew. Neither the captain nor the first officer checked the door status lights on the overhead panel or the EICAS display.
When the captain queried the tug driver regarding readiness, the driver stated that all service and cargo doors were secured and locked, with the exception of the jet bridge. The captain then authorized the pushback. During the maneuver, the tug driver signaled the wing walkers and initiated the movement, resulting in damage to the jet bridge, the L2 door, a section of the aircraft skin, and the L2 evacuation slide.
Findings
Following the incident, it was determined that the right wing walker had not provided the required "all clear" signal to the tug driver as mandated by company policy. Meanwhile, the left wing walker signaled that the ramp was clear under the assumption that there was an issue with the jet bridge, given that the captain had ordered the pushback to proceed.