An airplane and not a missile launch was the likely cause of a large vapour trail in the skies off Southern California's coast, the Pentagon has said.
A CBS television affiliate videotaped the vapour trail that many viewers thought resembled the cloudy track of a missile in flight.
But military officials said they did not know of any rockets being launched in the area on Monday.
Defence Department spokesman Colonel Dave Lapan said officials are satisfied the phenomenon was an airplane vapour trail distorted by camera angle, winds and other environmental factors.
He said military experts studied the video and talked to all the government agencies that might have been involved in a missile launch and none reported having launched one.