UAV - Unpiloted Aerial Vehicle
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (mon) 1
Confusion
ATC Issue All Types; Airspace Violation All Types; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance
Human Factors; Procedure
Aircraft X [a UAV] departed BAB and began a normal climb out to FL190 on their filed route of flight. As Aircraft X was leaving approximately 140 the pilot requested a left 360. I responded with 'Proceed as requested' and restated to maintain FL190. As Aircraft X was about halfway into the unplanned turn the pilot asked if they could rejoin their filed route of flight and climb to FL510 block FL590. I responded with 'Proceed as requested' and did not restate the altitude to maintain. At that point Aircraft X rejoined the filed route of flight and began a climb into ZOA airspace without coordination or communications transfer as the Aircraft X pilot missed the frequency change.I failed to restate the altitude to maintain on the second 'Proceed as requested' instruction. Additionally I will refrain from using 'Proceed as requested' with IFR aircraft as it can lead to confusion. I don't usually use that phraseology with IFR aircraft; but I felt that the pilot was a little confused and that giving them less complicated instructions would be more expeditious. In this case it led to confusion with the altitude and an airspace violation occurred.
NCT Controller reports of an aircraft that requested a 360 turn. The Controller used the term 'Proceed as requested.' The aircraft did and while halfway through the turn the pilot requested to rejoin the flight plan and climb to a higher than assigned block altitude. Controller again used the term; 'Proceed as requested;' but forgot to restate the altitude to maintain. Aircraft climbed through uncoordinated airspace leading to an airspace violation by the NCT Controller.