Date: 202007
Local time of day: 1201-1800
Location: ZZZ.TRACON, US
Flight conditions: VMC
Light: Daylight
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Descent
Airspace: Class E ZZZ
ATC / advisory: TRACON ZZZ
Second aircraft: Small Aircraft; High Wing; 1 Eng; Fixed Gear
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; Captain
Reporter qualification: Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Human factors: Distraction; Communication Breakdown
Second reporter function: Pilot Flying; First Officer
Anomaly: ATC Issue All Types; Conflict Airborne Conflict
Detector: Automation Aircraft RA; Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued Advisory / Alert; Air Traffic Control Separated Traffic; Flight Crew FLC complied w / Automation / Advisory
Contributing factors: Human Factors; Procedure; Aircraft; Airspace Structure
Primary problem: Human Factors

Narrative: While descending via the STAR; we were called out as traffic to Aircraft Y that had dropped its jumpers and was descending steeply back to their airport to the east of our arrival corridor. The aircraft was not called out to us as traffic but both the First Officer and myself had the aircraft in sight and determined its path not to be a threat to our flightpath. As the Cessna descended through our altitude; making counter-clockwise turns; we received a TCAS RA to 'LEVEL OFF' and the First Officer disconnected the automation and leveled the aircraft at approximately 8;000 ft. I communicated our response to the RA to the approach controller and within seconds of leveling off the RA extinguished and we resumed descending on the arrival without further incident.Aircraft descending VFR in close proximity to arrival corridor caused our TCAS to issue a RA. At no time did the approach controller alert us to the position of this aircraft; though both pilots had the Cessna in sight; and the controller never indicated to the Cessna that they should move away from the arrival corridor. Approach should more actively separate skydive aircraft from the STAR course when aircraft are descending on the arrival.


Second narrative: While on the RNAV STAR we were descending between 9;000 ft. and 7;000 ft. We heard Aircraft Y was on frequency and had just released skydivers. The aircraft was now in the descent for landing. Approach had just issued a traffic call informing the pilot of our aircraft heading northbound. The pilot said he had us in sight and would maintain visual separation. Approach then handed him over to advisory frequency. Close to only 1 minute later the descending Aircraft Y; was now passing through our altitude and was approximately 1 mile east of our aircraft. At this time we saw it bank hard into a left-hand turn; which placed him turning into our direction. Just before he banked into the turn we received a Traffic Alert from TCAS. Just after he banked in our direction our TCAS issued a Resolution Advisory which dictated to monitor vertical speed to close near 0 FPM descent rate. Although we had traffic in sight; I complied with the RA in case other factors I was unaware of were being considered by TCAS. We informed Approach we had received an RA because of the other aircraft and told them that we had indeed taken corrective action. We continued the approach and landing as normal.This event was caused by Aircraft Y electing to turn towards our aircraft while descending into his base of operations. Having already having told ATC he had us in sight I do not believe ATC made an incorrect decision to allow them to switch to advisory frequency prior to assuring that he posed no threat to our flight. Aircraft Y did not give enough space between his aircraft and ours.


Synopsis: Air carrier flight crew and TRACON Controller reported an airborne conflict for skydive operation aircraft which maneuvered too close to a commercial fixed winged aircraft.