Narrative:

I took this flight over when I accepted the desk. I remember asking the [supervisors] right away if they planned on operating flights to sjo at night with a SIGMET for vash so close to field. The plan was to operate because wsi SIGMET showed the vash just east/south east. I talked to the captain on the phone before departure and we had a good long briefing discussing the vash. We agreed to add a second alternate mainly mpto because we felt if there were any reports of vash at all even if SIGMET was still not on field we wanted options for airport to go and options with fuel. While flight was en route I was watching for any changes to the SIGMET. Wsi SIGMET was off the field however I made calls to the station as well as local ATC on numerous occasions to get updates. I asked about flights inbound and departures for any PIREPS to find out if anyone had encountered ash. We also had a few other desks at this time with flights in and out of sjo. Each time one left or landed sjo I was asking for PIREPS and no ash was reported. Before this flight started its approach I made another call to sjo local ATC to check on sjo conditions and for any reports of ash. The controller said airport was clear and no reports of ash. I made it a point to specifically ask for these things. After calls to local ATC and also no ash reported by our own flight that had landed a few hours prior to mine; I was confident my flight would not encounter ash. We even made sure to do the approach from the west since the ash SIGMET was east of field.I relayed all the information I had to the captain via ACARS before he started his approach. Had there been any report of ash I would have recommended divert. As it turned out; even though all of our other flights did not encounter ash; it was night time so apparently there was a cloud of ash that went well away from the SIGMET and was over a fix at the time my flight flew through north west of the field. The captain called after he landed he may have encountered ash but the way I understood it he wasn't sure. So I reported that to maintenance. I am not sure if the phone records are still available but if they are; I think I made at least 5 or more calls to station and ATC to get updates on field conditions. I made so many calls that others with sjo flights were asking me for updates. Based on the information I had at the time I was confident my flight was safe to continue.

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Original NASA ASRS Text

Title: Dispatcher reported a possible aircraft volcanic ash encounter during night cruise.

Narrative: I took this flight over when I accepted the desk. I remember asking the [supervisors] right away if they planned on operating flights to SJO at night with a SIGMET for VASH so close to field. The plan was to operate because WSI SIGMET showed the VASH just east/south east. I talked to the captain on the phone before departure and we had a good long briefing discussing the VASH. We agreed to add a second alternate mainly MPTO because we felt if there were any reports of VASH at all even if SIGMET was still not on field we wanted options for airport to go and options with fuel. While flight was en route I was watching for any changes to the SIGMET. WSI SIGMET was off the field however I made calls to the station as well as local ATC on numerous occasions to get updates. I asked about flights inbound and departures for any PIREPS to find out if anyone had encountered ASH. We also had a few other desks at this time with flights in and out of SJO. Each time one left or landed SJO I was asking for PIREPS and no ASH was reported. Before this flight started its approach I made another call to SJO local ATC to check on SJO conditions and for any reports of ASH. The controller said airport was clear and no reports of ASH. I made it a point to specifically ask for these things. After calls to local ATC and also no ASH reported by our own flight that had landed a few hours prior to mine; I was confident my flight would not encounter ASH. We even made sure to do the approach from the west since the ASH SIGMET was east of field.I relayed all the information I had to the captain via ACARS before he started his approach. Had there been any report of ASH I would have recommended divert. As it turned out; even though all of our other flights did not encounter ASH; it was night time so apparently there was a cloud of ASH that went well away from the SIGMET and was over a fix at the time my flight flew through North West of the field. The Captain called after he landed he may have encountered ASH but the way I understood it he wasn't sure. So I reported that to Maintenance. I am not sure if the phone records are still available but if they are; I think I made at least 5 or more calls to station and ATC to get updates on field conditions. I made so many calls that others with SJO flights were asking me for updates. Based on the information I had at the time I was confident my flight was safe to continue.

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.