I have seen the chemtrails do that and I have also seen them dissipate thunderclouds. Really weird too!

Also see “A Field Guide to the Atmosphere“, by Schaefer and Day, 1981:

“Sometimes [contrails] are ephemeral and dissipate as quickly as they form; other times they persist and grow wide enough to cover a substantial portion of the sky with a sheet of cirrostratus“ (Page 137)

I have seen some sites that debunk what we are seeing and since there are lies in text books then I have to wonder about other info as well. I know what my eyes see as well as my camera. Here are some pics I took that show a cloud being dissipated. All these shots were taken on 3-7-09 within a 10 minute span of the same cloud.