If the skies around LA are so busy, how come only 1 or 2 people in a helicopter reported a missile shot? IMHO this is the #1 reason to doubt the missile theory.
The fact that there are NO OTHER WITNESSES of the original event indicates that perhaps this did not look like a missile from other angles or to those who were able to watch it for a while.
The missile shot was heading northwest. It wasn't going over L.A.m it was heading away. It's safe to say that the vast majority of So Cal folks in the sightline of VAFB missile shots and San Nicolas shots don't notice them. Remember, too, that there are areas in the L.A. - O.C. county metropolis that aren't in much line-of-vision for missile launches and never see much of them at all but the tail end if they're lucky. Some of us, on the other hand, who've lived in direct line of sight not only notice them but love watching them with binocs when possible because they're so very, very cool to witness. Generally we're the kind of people who will grab binocs to look at any object in the sky that looks interesting or unusual.
That no other witnesses' testimony has been made public on broadcast media is easy for me to believe -- super easy, actually. On the other hand, that a sky-roving cameraman with 11 years' local experience and aided by professional zoom lenses confused an airliner contrail with a missile launch plume, is beyond the realm of believability.
Now: how about that five-word answer?
I posted a link to the SiteMonitor site where you can watch every single flight in LA airspace the entire day of the event. If you had bothered to look you would have seen that only two flights between 4:45 to 5:45 even came up from the southwest deep ocean into the Los Angeles basin. Two flights in one hour.