John Pike of the security analyst group globalsecurity.org said the video shot by a news helicopter owned by KCBS is an optical illusion.
Pike said the video is of an airplane heading toward the camera and the contrail is illuminated by the setting sun. He said the object can't be a rocket because it appeared to alter its course.
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Pentagon officials were stumped by the event, saying no one within the Department of Defense has been able to explain the contrail or where it came from.
The FAA told CBS News that they ran radar replays of a large area west of Los Angeles based on media reports of the location of a possible missile launch, but they did not reveal any fast moving unidentified targets in that area. The FAA also did not receive any reports of any unusual sightings from pilots in the area.
Missile tests are common off Southern California. Launches are conducted from vessels and platforms on an ocean range west of Point Mugu.
The North American Aerospace Defense Command, or NORAD, issued a statement jointly with the U.S. Northern Command, or NORTHCOM, saying that the contrail was not the result of a foreign military launching a missile. It provided no further details.
"We can confirm that there is no threat to our nation, and from all indications this was not a launch by a foreign military," the statement said. "We will provide more information as it becomes available."