In viewing the CNN coverage i can't make it out, i could in a film from another angle. What is very plainly visible is something firing out of the right side of the plane just before impact. It is not glare from the sun, it is very visible in other videos taken from behind (not this CNN shot though) but it shows here in the second view of the plane taken from the side, watch just after it goes behind the tip of that other building and before it hits WTC. Click onto full screen and you can replay it by pausing and moving the slidebar back.
http://www.cnn.com/video/us/2001/09/...s.cnn.med.html