Date: 202003
Local time of day: 0601-1200
Location: ZZZ.TRACON, US
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Descent
ATC / advisory: TRACON ZZZ
Second aircraft: Commercial Fixed Wing
Reporter organization: Government
Reporter function: Enroute
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Training / Qualification; Workload; Communication Breakdown; Confusion; Situational Awareness; Human-Machine Interface; Distraction
Anomaly: ATC Issue All Types; Conflict Airborne Conflict; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Separated Traffic
Contributing factors: Environment - Non Weather Related; Human Factors; Procedure
Primary problem: Procedure

Narrative: I was working [Sector X] and we had just combined our west side airspace. I was working X and Y sectors. According to our LOA; ZZZ was supposed to give us aircraft over ZZZ1 crossing 11 DME from ZZZ1 at 11;000. I had Aircraft X as an overflight to ZZZ2 at 9;000 and crossing roughly 5 or so miles east of ZZZ1. I took radar on Aircraft Y from west of ZZZ1 who was inbound for landing at ZZZ2; one of our satellite airports. 10 miles in trail of him was Aircraft Z also landing at ZZZ2. Aircraft Y checked on and said he was descending to 10;000. Aircraft Z also checked on descending to 10;000. ZZZ did not APREQ (Approval Request) descending; as both aircraft were not level when I took the handoff. They also did not APREQ the wrong altitude for direction of flight. There was zero coordination from ZZZ on these aircraft.We called to ask them to discontinue this practice and leave arrivals at 11;000. At first they agreed; but then proceeded to continue giving 10;000 with zero coordination. This continued throughout the night. When the midnight controllers started working; they again ran into the same issue with zero coordination and descended aircraft into our airspace. We tried again to tell ZZZ to discontinue this operation; but they refused and said they were instructed by their Operations Manager to give these aircraft 10;000. This was all taking place while ZZZ was ATC zero / ATC limited during the coronavirus pandemic. So we were working multiple overflights at 10;000 westbound while ZZZ was assigning 10;000 to eastbound arrivals with zero coordination. This was a very dangerous practice and with no coordination we were lucky this didn't result in any losses of separation. Luckily at the time; my overflight Aircraft X was at 9;000 and I was able to verify Aircraft Y's altitude and made sure he was stopping above. They got within 6 miles of each other; with a closing speed of over 600 kt. This entire operation from ZZZ; being ATC zero and ATC limited; has been handled very poorly. ZZZ has refused to comply with our contingency plan and we have been stuck with only 10;000 and below. I know this is a dynamic situation and we are not used to this. However; it should not mean that ZZZ can just throw our contingency plan as well as the 7110.65 out the window. I would recommend ZZZ [to] comply with the contingency plan. I would also recommend ZZZ [to] comply with the 7110.65 regarding altitude for direction of flight and approval requests. We have an ongoing problem with ZZZ being unable to comply with LOA's and it's starting to become a dangerous situation. As of [this] date and time; ZZZ is still not complying with the contingency plan.




Synopsis: TRACON Controller reported problems with overlying Center not complying with LOA and the contingency plan.