Small Transport; Low Wing; 2 Recip Eng
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 14
Situational Awareness; Distraction; Confusion; Communication Breakdown
ATC Issue All Types; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued New Clearance; Flight Crew Returned To Clearance
Procedure; ATC Equipment / Nav Facility / Buildings; Human Factors
Merida center coordinated Aircraft X at IPSEV at XA:00 at 100 and Aircraft Y at IPSEV at XB:01 at 140. No radio [communication] is available at those altitudes. Subsequently; Aircraft Z relays a non-radar position report for Aircraft X; crossed IPSEV at XB:10 at 140. He was coordinated at 100. I double verified the info. Thinking Merida had gotten the altitudes switched; I waited for a position report on Aircraft Y; with none coming. I asked Merida if they still had their coordination info on these planes and he said no. I then got Aircraft A to relay through Aircraft X to get a report from Aircraft Y; and got a position report of IPSEV at XB:06 at 140. I had Aircraft A relay to Aircraft X to descend to 120; Aircraft X said he wanted to stay at 140 due to advantageous winds. I said we can't do that in non-radar; and he had to descend. He requested 100; and I had him descend to 100. (All of this relayed back and forth through Aircraft A). I was working the Ocean West airspace by myself during this; so there were some minutes of delays between the steps; the total elapsed time being 17 minutes. In short; Aircraft X was supposed to be at 100; but showed up at 140. I theorize that he climbed on his own to get in better winds and didn't tell us. He was later told 'possible pilot deviation' and told to contact us.I recommend that pilots get a clearance before they change altitudes.
A ZHU Center Controller reported of having an aircraft at the wrong altitude. The aircraft climbed to an altitude it was not supposed to and a conflict arose with another aircraft. The reporter called the other center for information but they did not have any. The controller had to relay through a third aircraft to get things straightened out.