Hello, colleagues,
This is Masayuki Shiraishi, the person himself who took the photos and movie of something glittering over a plane wing last year, just one year ago.
I've considered the phenomenon but I have no idea.
Yesterday, I found this thread and I knew that you all had discussed the phenomenon.
If this thread is still open, I will add some information.
The flight was
LX161 of Swiss International Air Lines, NRT (Japan) to ZRH (Switzerland), as Mick mentioned (correct!).
The date of flight was
October 10, 2016; and the time that the phenomenon appeared was
10:48 UTC+9.
It was about 20 minutes later from the departure. Typical departure time is 10:25 UTC+9.
I think it was over the Japan Sea, but at that time I could not see the sea because clouds spread under the plane.
At first I noticed that something glittering over the wing
by naked eyes.
It was apparently outside of the plane.
Then I tried to take some photos of them, however, glitter was too quick to be captured a single shot.
So I took a short movie so that I can stack the multiple frames from the movie later.
This phenomenon continued only one or two minutes.
After that, a vapor line appeared from the wing tip (10:49), see the following photo.
After the glitter disappeared, the wing tip vapor line continued for several minutes.

Later I found that there were 2 arcs over the wing, by the stacked image.
On flight, I saw only one glittering arc (larger one). The other one could not be recognized by naked eyes.
My seat was
36K, the right window-side, a little rear of the right wing.
(I love taking photos outside of plane's window; terrain, clouds, dusk and dawn, night stars, airplane glories...)
A rough estimation of the position, direction, and sunlight direction was shown below.

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So, the line of sight was approximately opposite of the Sun.
If they are flying ice crystals, I think the angular condition among the Sun, crystals, and me is also related.
They will reflect sunlight within a narrow path flaring to me, like an Iridium flare.
Some people suspect something on double window panes, but I don't think so.
The panes are too close to be resolved in these images.
This photo and movie were taken in F10, and the distance between the wing tip and me was about 25 meters (A343-300). I set auto-focus at the wing tip. In this case, the depth of field is 1.7 meters (near) to infinity (far).
So, anything between window panes and any scratches on window panes can not be resolved.
And anything 1.7 meter or farther from me could be in focus.
This is just as Mick mentioned.
This thread contains interesting discussion.
If they are ice crystals, why is it rare...?
I searched for similar phenomena's photos, reports, and descriptions, but I could not find...
I'm sorry for my poor English.
Best regards,
Shiraishi