Narrative:

I was working sector 29 by myself at a level of traffic that I wouldn't need a d-side. A call comes in blocking an aircraft checking on. There is an aircraft on the suttr arrival into smf level at FL190 but descending via; far as I know. I was not talking to the second aircraft. Aircraft X attempted to check on when I was coordinating he leveled at FL190. He then checks on again telling me he sees traffic at his altitude and needs to climb. Norcal approach shipped the aircraft late or he attempted to check on multiple times while being stepped on or not heard due to coordination. Would having a D side made the situation better yes of course did I need one; I would say not. Aircraft X finally checks on I immediately climb and turn the aircraft seeing it will be really close to or less than 3 miles. The turn and the immediate climb saved the loss of separation; the aircraft reported out of FL200 before he hit the 3 mile ring. Norcal approach should maybe have asked for higher in this situation or descended the suttr arrival in the event the aircraft couldn't check on; which is what ended up happening. After watching the falcon no loss was seen; and when I was working the plane reported out of FL200 outside of the 3 mile ring. Norcal should or could've asked for higher. The pilot was definitely not happy about be so close to the other plane and climbed and reported out of FL200 very rapidly. Should those airplanes on the suttr level at FL190 when departures are climbing out and possibly losing communication at FL190 probably not.

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Original NASA ASRS Text

Title: ZOA Center Controller reported an unsafe situation when an aircraft was switched over from NCT TRACON and the pilot took it upon himself to climb to avoid traffic at the same altitude.

Narrative: I was working Sector 29 by myself at a level of traffic that I wouldn't need a D-side. A call comes in blocking an aircraft checking on. There is an aircraft on the SUTTR arrival into SMF level at FL190 but descending via; far as I know. I was not talking to the second aircraft. Aircraft X attempted to check on when I was coordinating he leveled at FL190. He then checks on again telling me he sees traffic at his altitude and needs to climb. Norcal approach shipped the aircraft late or he attempted to check on multiple times while being stepped on or not heard due to coordination. Would having a D side made the situation better yes of course did I need one; I would say not. Aircraft X finally checks on I immediately climb and turn the aircraft seeing it will be really close to or less than 3 miles. The turn and the immediate climb saved the loss of separation; the aircraft reported out of FL200 before he hit the 3 mile ring. Norcal approach should maybe have asked for higher in this situation or descended the SUTTR arrival in the event the aircraft couldn't check on; which is what ended up happening. After watching the falcon no loss was seen; and when I was working the plane reported out of FL200 outside of the 3 mile ring. Norcal should or could've asked for higher. The pilot was definitely not happy about be so close to the other plane and climbed and reported out of FL200 very rapidly. Should those airplanes on the SUTTR level at FL190 when departures are climbing out and possibly losing communication at FL190 probably not.

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.