In the early 1950`s contrailing B36s & B47s were a regular sight over N Yorks. B36s used to make mantelpiece ornaments vibrate! I believe that the local Sabres from Linton on Ouse, 66 &92 Sqns did have difficulty carrying out practice interceptions on the B36 at high altitude. The SAC film was so evocative,especially the sound as a B36 flew over the baseball game!!