Narrative:

I observed a loss of standard separation between sdf arrival; aircraft X; and an ind departure; aircraft Y in sector 34/35 airspace. Conflict alert made me aware of the situation in the adjacent sector's airspace. I did not talk to either aircraft at any point. Aircraft X was on a flash through procedure described in the SOP whereas; sdf arrivals will be issued 110 at frizn. The aircraft was flashed to me; I accepted the hand off and having no traffic; flashed aircraft X to louisville approach. I resumed my scan and a short while later saw conflict alert go off. Both aircraft were with the altitude stratum of 34/35 and being controlled by them as best I could tell.I immediately observed the ind departure; aircraft Y; have present heading entered into the data block and observed a turn. I continued with my scan as the aircraft were neither in my airspace nor on my frequency. My supervisor was observing the situation over my shoulder and requested I place a halo on aircraft X. Shortly after we observed the aircraft Y issued 170 as an altitude which the aircraft had already climbed through and was now descending. Aircraft X never appeared to turn but did appear to level at FL180. When aircraft X was at FL181 aircraft Y appeared to enter the halo at 173; passing behind aircraft X. Again I observed the situation only as it did not occur in my airspace or with any need to speak to either aircraft. Witnessing 'ph' (present heading) in the data block; observing the beginning of a turn and the issuance of an altitude led me to believe the conflict was actively being addressed.it is possible that the flash through played a role in the situation; however I do not know what was occurring in that sector. From my perspective it appeared that either performance or speed was underestimated and that the control instructions issued did not occur as was anticipated.

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Original NASA ASRS Text

Title: ZID Controller reported observing a loss of separation between two aircraft that he was not working and in another Controller's airspace. Reporter stated the flash through procedure may have contributed to the event.

Narrative: I observed a loss of standard separation between SDF arrival; Aircraft X; and an IND departure; Aircraft Y in sector 34/35 airspace. Conflict alert made me aware of the situation in the adjacent sector's airspace. I did not talk to either aircraft at any point. Aircraft X was on a flash through procedure described in the SOP whereas; SDF arrivals will be issued 110 at FRIZN. The aircraft was flashed to me; I accepted the hand off and having no traffic; flashed Aircraft X to Louisville approach. I resumed my scan and a short while later saw conflict alert go off. Both aircraft were with the altitude stratum of 34/35 and being controlled by them as best I could tell.I immediately observed the IND departure; Aircraft Y; have present heading entered into the data block and observed a turn. I continued with my scan as the aircraft were neither in my airspace nor on my frequency. My supervisor was observing the situation over my shoulder and requested I place a halo on Aircraft X. Shortly after we observed the Aircraft Y issued 170 as an altitude which the aircraft had already climbed through and was now descending. Aircraft X never appeared to turn but did appear to level at FL180. When Aircraft X was at FL181 Aircraft Y appeared to enter the halo at 173; passing behind Aircraft X. Again I observed the situation only as it did not occur in my airspace or with any need to speak to either aircraft. Witnessing 'PH' (Present Heading) in the data block; observing the beginning of a turn and the issuance of an altitude led me to believe the conflict was actively being addressed.It is possible that the flash through played a role in the situation; however I do not know what was occurring in that sector. From my perspective it appeared that either performance or speed was underestimated and that the control instructions issued did not occur as was anticipated.

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.