What are those dark lines on the windows?

Boarded an A321 of Peach airlines. Saw some dark lines appearing on the windows.

What are they? Dust marks?

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Same thing happens on my travel trailer. Water along with dirt and maybe a bit of black rubber gasket from around the window.

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Reflection of beach.....

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Well, it was! This was an offshore airport.

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peach! cutest low cost airline livery

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Dirt

It’s a dirty girl

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Probably caused by water.

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Must be the water.

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Or reflection of tail ....

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Flying through dust then landing in mist or light rain.

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Looks like a dusty plane landed in some rain or moisture and the dust collected where the water trails off the body of the plane.

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Why only in those spots? Windows on the front doesn't have any.