Narrative:

Aircraft Y and aircraft X were refueling blocking altitudes 24;000-26;000 feet. Aircraft Y requested 32;000 feet via cpdlc. I advised aircraft Y to report at the top of the altitude block and vertically separated from aircraft X. Aircraft X advised via HF radio that they made a right turn and were requesting 37;000 feet on flight plan route. Controller requested a position report from aircraft X. The position report indicated that aircraft Y and aircraft X were about 100 miles apart and flying opposite direction. It appears that aircraft X left refueling block and was returning to [base] without an ATC clearance. Brasher warning was given to aircraft X.this is the third time I have experienced a pilot deviation like this from a tanker in this ARTCC. I would recommend training for military pilots on what their requirements and responsibilities are for military authority assumes responsibility for separation of aircraft (marsa) and refueling operations. They don't seem to understand that they must have a clearance to alter their routing.

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Original NASA ASRS Text

Title: An aircraft in a refueling track departed the refueling track and began its flight back to its base without a clearance.

Narrative: Aircraft Y and aircraft X were refueling blocking altitudes 24;000-26;000 feet. Aircraft Y requested 32;000 feet via CPDLC. I advised aircraft Y to report at the top of the altitude block and vertically separated from aircraft X. Aircraft X advised via HF radio that they made a right turn and were requesting 37;000 feet on flight plan route. Controller requested a position report from aircraft X. The position report indicated that aircraft Y and aircraft X were about 100 miles apart and flying opposite direction. It appears that aircraft X left refueling block and was returning to [base] without an ATC clearance. Brasher warning was given to aircraft X.This is the third time I have experienced a pilot deviation like this from a tanker in this ARTCC. I would recommend training for military pilots on what their requirements and responsibilities are for Military Authority Assumes Responsibility for Separation of Aircraft (MARSA) and refueling operations. They don't seem to understand that they must have a clearance to alter their routing.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.