Large Transport; Low Wing; 2 Turbojet Eng
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 4.0
Communication Breakdown; Situational Awareness; Confusion
ATC Issue All Types; Conflict NMAC; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Took Evasive Action
Airspace Structure; Environment - Non Weather Related; Human Factors; Procedure
Aircraft X was proceeding south into Havana airspace. I issued Aircraft X a Pilot's Discretion descent to 25000 feet from 31000 feet. The controller from Havana called and requested control of Aircraft X for direct to destination. I released control and coordinated that the aircraft was given pilots discretion descent to 25000 feet. At the same time; Aircraft Y was proceeding over northbound. Aircraft Y was level at 30000 feet and I anticipated the aircraft to be descending to 24000 feet. The Havana controller asked if I had radar contact with Aircraft Y and I replied in the affirmative. I proceeded to transfer communications of Aircraft X to Havana so they could turn the aircraft direct or if they needed to amend the altitude clearance I had given. As Aircraft X progressed the aircraft was still at 31000 feet and still on route. Aircraft Y was still at 30000 feet and still on route. Shortly after; both aircraft began descending maintaining the 1000 ft separation. Then Aircraft X began to increase its rate of descent until separation was lost and they were still head on. I called for Aircraft Y to see if he was on my frequency so I could ensure that he was aware of the traffic. Aircraft Y did not answer. In the meantime; low controller was calling Havana to ask if they were aware of the conflict. They informed me that there was no answer from the Havana controller. I then saw Aircraft Y quickly climb. I am not sure if it was due to an RA or a control instruction from Havana. The two aircraft merged head on with only about 200 feet separating them. It later came to my attention that when Havana had called to request control of Aircraft X; they never said that the aircraft was radar contact and I never initiated a radar handoff. I understood that the aircraft was radar contact; but it was never said on the line. I would recommend paying closer attention to the words used and to ensure that either Havana or ZMA is taking responsibility to separate the two aircraft. I would also make a change in the procedure that states whoever calls the foreign facility will be responsible for initiating a radar handoff. Confusion is created when a facility calls and requests control for an aircraft approaching their boundary and does not take radar contact. Since they didn't use the control that they requested; it would have been better not to make the call. I would have then called Havana to handoff Aircraft X and they could have requested control at that time.
ZMA Controller received a call from Havana to coordinate and hand off southbound traffic entering their airspace. ZMA Controller observed the aircraft and another northbound aircraft in Havana airspace descending. The targets merged with 200 feet of vertical separation in Havana airspace.