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Strange thing on flight from Szczecin to Krakow?

• Hi, Earlier this week I took a domestic flight in Poland from Szczecin (North) to Krakow (South). The flight was about 40 minutes in and I saw out of the window a black thing zoom from another plane in the distance and fly up into the atmosphere, leaving what looked like a smoke trail behind it. I have no idea what it was - I thought maybe the other plane could have expelled something, but surely it would fly downwards (gravitational pull) than fly UP into the atmosphere? Can anyone explain? :) Thanks

• Answer:

  There are quite a few things that possibly caused this phenomenon. Since you specifies you saw it being expelled from another plane there is the high possibility it was the normal release of waste that occurs at various times throughout a flight. Whatever it exactly was being expelled from the plane, it would be normal for it to go upwards in the atmosphere first because of speed, velocity, and momentum.