Date: 201807
Local time of day: 0001-0600
Location: ZNY.ARTCC, NY
Light: Night
Aircraft: B737-700
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Descent
Airspace: Class A ZNY
ATC / advisory: Center ZNY
Second aircraft: Global Express (BD700)
Reporter organization: Government
Reporter function: Enroute
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Communication Breakdown; Situational Awareness; Workload
Second reporter function: Enroute
Anomaly: ATC Issue All Types; Conflict Airborne Conflict; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Automation Aircraft RA; Person Air Traffic Control; Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued Advisory / Alert; Air Traffic Control Issued New Clearance; Air Traffic Control Separated Traffic; Flight Crew FLC complied w / Automation / Advisory; Flight Crew Took Evasive Action
Contributing factors: Company Policy; Staffing; Procedure; Human Factors
Primary problem: Procedure

Narrative: I was working towards the end of a 10 hour overtime shift. We were extremely understaffed this night; with no supervisor on the shift. The shift was published 2 under the number with the Supervisor previously assigned to the shift approved to go on a detail. The shift ended up 4 controllers under staffed. Towards the end of my 10 hour overtime shift we had several controllers; myself included that needed to be relieved from their position because it was the end of their shift. We had to combine sectors to be able to get people up for the end of shift. After combining the sectors I had Aircraft X landing. I then issue a crossing restriction of 65 NM W of a fix at 27000 feet. After reviewing the tapes; it turned out I missed the read back of 25000 feet instead of 27000 feet. Then it was my turn to be relieved from position. During my relief overlap time I'm watching my relieving controller take a handoff on Aircraft Y climbing to 26000 feet opposite direction of Aircraft X. The controller issued a traffic call to Aircraft X and Aircraft Y with more than 15 miles. Aircraft X initially acknowledged the call without question. After a few seconds Aircraft X got an RA to climb and then questioned the traffic call. The relieving controller took action to reestablish positive separation. Controllers at the end of a 10 hour shift should probably not be working combined sectors with above average volume and complexity. There should be supervision on every shift to monitor these type of scenarios. The Pilots should have questioned a traffic call with an aircraft climbing through his altitude.


Second narrative: Sector 42 was just combined with Sector 56. I was instructed to relieve CPC on position so he can go home from a 10 hour overtime day. The current shift staffing was 4 under with no supervisor on duty. The cru-art was not up to date and there were multiple sessions of 2 plus hours working moderate to heavy traffic. CPC briefed me that Aircraft X received a crossing restriction descending to FL270. I took radar on Aircraft Y opposite direction climbing to FL260. I issued traffic to both aircraft approximatley 15 miles apart. Both aircraft acknowledged the initial traffic call. At 7 miles opposite direction Aircraft X questioned his clearance and advised me he was descending to FL250. I immediately turned Aircraft Y to a 240 heading to mitigate the loss of separation. Aircraft X received and RA and climbed back to FL270. I instructed Aircraft X to proceed direct HTO VOR when able.ZNY needs to be properly staffed in a timely matter. Area B worked -4 under the agreed upon staffing numbers. Additionally; there was no supervisor present for the entire shift. There needs to be a more timely thorough process to mitigate these challenges.


Synopsis: Center Controllers reported an aircraft conflict due to a missed altitude assignment read back at the end of a 10 hour shift.