"The plane was over water when the pilot said he saw a smoke trail pass by the cockpit.
FBI agents believe it was a flare or a bottle rocket, but say they may never know if that's what it actually was."
Anyone care to tell me what flare or bottle rocket can pass a jetliner? Hmmmmm?
I emailed a guy at the So Cal Rocket Assoc. and this is his reply: "I can tell you that a model rocket (no bigger than 2 x G motors) could not reach 6000 ft unless it was very small in weight and drag to achieve maximum altitude. In addition, there are no legal launch sites anywhere near the takeoff path from LAX. (Same for the landing glide path)."
Passing by doesn't mean it caught up to it in flight, it merely means that the device was near the aircraft at some point in their trajectories. Most likely the passing was in the vertical dimension. Both flares and bottle rockets could have a higher rate of climb than an airliner, at least for a very short period. Especially an airliner mainly trying to get away from land, but not trying to gain too much altitude (IE. Noise abatement procedures).