Narrative:

I was the flying pilot and on the runway heading during climbout when I observed; very momentarily out the captain's window; a very faint 'smear' of vertical lights north of our position. At the moment; I attributed the sighting to a light reflection or distortion effect and gave it no further thought as I was flying and calling out reconfiguring of the aircraft (I made no note of this to the crew as we were in sterile cockpit conditions and it seemed very anecdotal). We started towards the next fix on the SID when we were given a clearance of direct. When we rolled out on this heading; I looked ahead and noted that the lights that I sighted earlier were still present and at our 12 o'clock and we appeared to be on a collision course. The captain and the international relief officer were not immediately able to sight the object. I told the captain that I was deviating to the left of course to avoid the lights. About 3-5 seconds later we passed; abeam what we determined was a lighted; large balloon at our altitude (10;000 feet). I saw as we passed a very faint; indistinct light that had a string of illuminated lights running down what may have been one of the ropes attaching the gondola/instrument package to the gasbag. My best guess is we missed the object between 1/2 to perhaps 1 mile at most. ATC was not aware of the threat and seemed confused upon the captain's report of the incident. The object did not show on TCAS and so presumably was not transponder equipped. We reported the incident to dispatch; there were no further issues during the flight. I would add that had we not adjusted course that we most likely would have had a catastrophic inflight collision incident.

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Original NASA ASRS Text

Title: Two air carrier First Officers reported during climb from SBGR airport taking evasive action to avoid a balloon.

Narrative: I was the flying pilot and on the runway heading during climbout when I observed; very momentarily out the Captain's window; a very faint 'smear' of vertical lights north of our position. At the moment; I attributed the sighting to a light reflection or distortion effect and gave it no further thought as I was flying and calling out reconfiguring of the aircraft (I made no note of this to the crew as we were in sterile cockpit conditions and it seemed very anecdotal). We started towards the next fix on the SID when we were given a clearance of direct. When we rolled out on this heading; I looked ahead and noted that the lights that I sighted earlier were still present and at our 12 o'clock and we appeared to be on a collision course. The Captain and the IRO were not immediately able to sight the object. I told the Captain that I was deviating to the left of course to avoid the lights. About 3-5 seconds later we passed; abeam what we determined was a lighted; large balloon at our altitude (10;000 feet). I saw as we passed a very faint; indistinct light that had a string of illuminated lights running down what may have been one of the ropes attaching the gondola/instrument package to the gasbag. My best guess is we missed the object between 1/2 to perhaps 1 mile at most. ATC was not aware of the threat and seemed confused upon the Captain's report of the incident. The object did not show on TCAS and so presumably was not transponder equipped. We reported the incident to dispatch; there were no further issues during the flight. I would add that had we not adjusted course that we most likely would have had a catastrophic inflight collision incident.

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.