Comment: Probably flares

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Probably flares

When they are in a straight line it is obvious from the moment the were deployed. After that they just fall and go wherever the wind takes them. The triangle shape is formed because some fall faster then others and of course people are hardwired to see shapes in everything.
Just as we can see shapes in clouds. From another perspective it is almost certain not a recognizable 'formation'.
If they would fly away with enormous speed however, then i would be calling it a ufo.