It just fascinates me the lines that are created in the sky by airplanes. This morning was a bright blue sky with lines all over it. The thinner ones are of current planes flying their paths while the ones that are a little fatter and feathery are from planes long gone from the area, but having left their mark of where they have been. It is much like us people...we want to make a mark of where we have been on our path to wherever it is we are going.
I wish you further successes in photography!
Be happy!