A recent flight experience

I was traveling from New orleans to stlouis and the pilot came on and announced flight attendents to jump seats. I assumed that we would experience turbulence and thats why the announcement was made.. i looked at the flight attendant who was in the middle of coffee service and she looked worried. The flight attendents never sat down and continued with coffee.. as i looked out the window after about two minutes we flew through a sparse fog like cloud and i noticed a straight line “chem trail” with a definite black spot at the end of what I could see. The spot did not move. We basically flew eye level through the trail/tunnel . This picture is AI produced and is the closet to what I could get it looked like. I believe we were Over Alabama airspace.. definitely a weird sight that I’ve never seen before.. we never experience any turbulence.. I will be looking out the windows with my camera next time I hear the “jumpseat” message