I suppose it enters in the compartment "Hyperdimensional UFO Maneuvers", because it seems to be/appear in a +- area of the Colima's volcanoe, images captured by the same webcam timelapse, different days.
1006.jpg- March 29, 2015 http://www.webcamsdemexico.com/webcamtimelapse.php?a=a&c=89&f=2015-03-29, at 10:06:03 am, is not observable in other shots.
Saw it first here: _https://www.youtube.com/watch?v=m4T2Pf_ar9U (English)
724.jpg- April 18, 2015 http://www.webcamsdemexico.com/webcamtimelapse.php?a=a&c=89&f=2015-04-18, at 07:24:03 am, is not observable in other shots, is more blurred.
Saw it first here: _https://www.youtube.com/watch?v=20IBBuWv49c (music)
There is another video, _https://www.youtube.com/watch?v=YzKBuM5W24g that do not have time to see it right now, but, at the beginning, it has another capture another UFO at the same webcam site. --Will have to come later to see the whole video.
1808.jpg- Last image, February 23, 2015, at 18:08:02 pm http://www.webcamsdemexico.com/webcamtimelapse.php?a=o&c=89&f=2015-02-23
I do assume much that it is an UFO, and not anything else, of course, things are going crazier, so it can be anything else, still it is seen volume in two images.
edit: add: curoiusly, the three of them have the same inclination