I was returning home from vacation. The plane started to reduce flight. I took a few pictures by my phone because of nice clouds around. I did not see anything special. I did not notice UFO. When I got home I started watching photos I took. Then I have noticed thin line at the picture I have sent you. When I zoomed in at the end of this line I have realized that this is something unusual. Important - attached original photo should be seen on display with pixel density at least 300.