The relevant question is not how many flights were coming from the same direction, but how many people in the entire LA airspace were in a position to see the contrail/plume seen by the news helicopter. These people/aircraft could be travelling in any direction that would allow viewing of this from their windows.
Since some of the helicopter shots show land, it is clear that one did not have to be far out over the deep ocean to witness this phenomenon.
There are numerous witness reports. A Los Angeles Times story has a women in San Pedro that saw it from her backyard. She would have been close to that land the Helicopter showed. Also there are witness comments on some of the MSM stories and blogs. Even have a second video of what appears to be the same event.
If the missile was launched from San Nicolas Island, it was actually 50 miles out to sea and headed westward at a 45 degree angle. Not easy to spot. We also had a cold weather system that just blew in off the coast which is why you see clouds in the video and images. Flight AWE808 came through the launch area before the launch. No way they could have seen it. UPS902 came through around the time of the launch, but they were above 30,000 feet. Over San Nicolas Island at about 5:25 pm. So the missile would have launched 10 minutes before they got there and the missile would have been far west of that location by the time they got over that island. The Helicopter Pilot I think also said he looked over at another planes contrail why he was watching the event. That might have been UPS902.