N67/051.
I suggested following explanation:
MRS. DUNN was driving and unable to match cloud continuously. At one point when she looked back up at the sky she had lost sight of the original small white cloud and she was caught by the forming vapour trail of a high flying jet. What is the vapour trail was just beginning and was of a similar size and colour to her original little cloud. The elongation and motion was simply the configuration of the aircraft's motion at the time. The vapour trail was of less rapid diffusion and disappearance at the rear end of the vapour trail.
SKETCH HERE
SHORT ALONG THE EDGE
OVERHEAD
GAL. 104 METEOR CENTRE NATIONAL RESEARCH COUNCIL OTTAWA 8, ONTARIO
National Research Council of Canada/ RG 77, Vol. 306
Conseil national de recherches du Canada