Date: 202104
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Daylight
Aircraft: B737-800
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Parked
Aircraft component: Fuselage Skin
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Human factors: Communication Breakdown; Training / Qualification; Troubleshooting
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural MEL / CDL; Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: Aircraft In Service At Gate; Routine Inspection
Result: Aircraft Aircraft Damaged; Flight Crew Overcame Equipment Problem; General Flight Cancelled / Delayed; General Maintenance Action
Contributing factors: Aircraft; Human Factors; MEL; Procedure
Primary problem: MEL

Narrative: During walk-around; [the] FO (First Officer) found a dent in [the] aircraft; aft left side; near lavatory service. [The case was] entered into [the] AML and [we] informed Maintenance. Contract Maintenance took pictures; detailed measurements; and notes for submittal to ZZZ2 Maintenance Control. After approximately an hour; it was determined that [the] aircraft was good to go; item was deferred; and the paperwork was completed. Flight was uneventful to ZZZ1. At the gate in ZZZ1; a Mechanic came out to the aircraft with some ACARS paper that was requested inbound. We mentioned the dent; so he said he would go take a look. During this time; [the] aircraft was serviced; passengers were boarded; and the flight was 'ready' for departure. The door was actually closed when the Crew Chief informed us that we were on a maintenance hold. The same Mechanic returned and told us that the dent was very significant and the aircraft should be taken out of service for repairs. He mentioned that the aircraft shouldn't have flown and was a 'blowout' waiting to happen. A Maintenance Supervisor came out; evaluated the situation; and the aircraft was subsequently taken out of service. Why and how was it determined that the aircraft was 'good to go' at an outstation; but when the plane gets to a hub it's taken out of service? I understand a forward-leaning mentality when it comes to serving our passengers but this should never be at the expense of safety. We were informed by the Maintenance Supervisor that the discrepancy was deferred in ZZZ but the aircraft was to undergo further evaluation when it arrived in ZZZ1. This sounds plausible; except; the only reason the discrepancy was 'further evaluated' was because we needed ACARS paper and happened to mention the dent to an experienced and highly trained Mechanic; who applied the brakes to this situation. Mistakes can happen; but in situations where there is doubt regarding airworthiness; it is better to err on the side of caution.




Synopsis: B737 Captain reported confusion and miscommunication led to a flight with a damaged aircraft that was later found to be beyond proper limits and unairworthy.