Date: 201909
Local time of day: 1201-1800
Location: TJSJ.Airport, PR
Flight conditions: VMC
Light: Daylight
Aircraft: A321
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Climb
Airspace: Class B TJSJ
ATC / advisory: Center TJZS
Aircraft component: Exterior Pax/Crew Door
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Second reporter function: Pilot Not Flying; First Officer
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Landed As Precaution; Flight Crew Diverted; General Flight Cancelled / Delayed; General Maintenance Action
Contributing factors: Procedure; Aircraft
Primary problem: Aircraft

Narrative: During climb-out at about 15;000 ft.; a Flight Attendant from the aft cabin called to report that the 4R door had a very loud whistling/squealing sound; like an air leak. They had just flown the aircraft in and it did not sound that way for that leg. I could hear it clearly through the intercom. We checked the pressurization system; it was working fine. We leveled off early and called Dispatch who initiated a phone patch with Maintenance. Due to weather approaching the field; and the potential need for customs; we all agreed that the best course of action was to divert to SJU and perform an overweight landing. The First Officer and I briefed threats; the descent and approach; along with the overweight landing considerations. We did not [Request Priority Handling]. The landing was soft and uneventful. I wrote up the air leak issue and the overweight landing in the [Logbook]. Maintenance pulled the landing data and signed off the jet for the overweight landing; no inspection required. After speaking with Dispatch on the ground we discovered that we should have [Requested Priority Handling] which we missed as part of the brief. There was a time element involved due to impending weather at the field. After the call with Dispatch/Maintenance; briefing the passengers and crew; then briefing and programming the approach we received a runway change due to a wind shift. Overall everything went well and it was a safe operation; but we needed to be more aware of the details in the QRH that were missed due to the timing of the events and our oversight. I spoke with a member of the Estimated Return to Service the afternoon after this incident. That was the earliest I could contact someone due to the ferry flight we were assigned the next morning and the deadhead home.


Second narrative: Approximately 15 minutes after departure from ZZZ in the vicinity of ELOPO intersection during the climb phase of flight; a Flight Attendant notified the Captain that a loud noise was emanating from the right rear cabin exit door. The noise was similar to a loud whistling or squealing. The Captain as the flying pilot transferred the aircraft controls and radios to the FO (First Officer). The FO coordinated with Center for a lower cruise altitude. After consulting with the cabin crew; FO; Maintenance; and Dispatch; the Captain elected to divert to SJU. He continued to receive periodic reports from the cabin crew while keeping the passengers and Dispatch informed of the situation. SJU was using Runway 10 and was vectoring arriving aircraft to avoid a thunderstorm that was west of the airport. As we approached SJU the flight controls were transferred back to the Captain for the landing. After the landing; the aircraft was taxied to the gate for evaluation. After landing we learned that we should have [Requested Priority Handling].


Synopsis: A321 flight crew reported reported a whistling noise from the R4 door; causing a diversion.