Look up, way up and you will most likely spot a jet plane in the stratosphere. You don’t really hear them since at that height they are relatively quiet and as a result they do not disturb a peaceful walk in the park. I enjoy the contrast of walking in the park, observing nature on the ground and looking up at the clear blue skies above as a jet plane zooms by. The white trails or contrails left by jet planes can take your breath away. These trails are created when engine exhaust combines with the atmosphere at high altitude.