Mystery 'missile' launch in US: the theories
The condensation trail, or contrail, of an apparent missile launch off the coast of California west of Los Angeles has prompted speculation as to what might have caused it. Here are some of the theories.
Doug Richardson, the editor of Jane's Missiles and Rockets, said it might have been a Standard interceptor, the anti-missile weapon which is fitted to the US Navy's Aegis guided-missile cruisers as part of the American missile defence programme.
He said: "It's a solid propellant missile, you can tell from the efflux [smoke] but they're not showing enough of the tape to show whether it's staging [jettisoning its sections]."
Robert Ellsworth, the former US Deputy Secretary of Defence, said it was "pretty big" but "not a Tomahawk" cruise missile.
He said: "It could be a test firing of an intercontinental ballistic missile from a submarine to demonstrate to Asia that we can do that."
US President Barack Obama is presently on tour in Asia and gave a speech in Jakarta, in Indonesia, on Wednesday.
The authorities have examined their radar records to check that no foreign power was behind it. Last week, the Japanese Navy test-fired an American Standard interceptor from one of its Kongo-class guided-missile destroyers off Kauai, in Hawaii, but there were no known plans for another test this week.
Others have speculated that it could be a target which was launched to test anti-missile lasers which are currently being developed and do get trialled in the Pacific.
There have even been those keen to announce it as an alien UFO.
A more down-to-earth - and non-military - explanation was given by John Pike, director of the US-based security analyst firm globalsecurity.org.
He said: "The local station chopped up the video and so it's hard to watch it continuously but at one place you can see it has changed course - rockets don't do that."
He added it was most likely to be a normal aircraft contrail which appears different in the sun: "It's an airplane that is heading toward the camera and the contrail is illuminated by the setting sun."
Others have claimed it could be the work of amateur missile enthusiasts. In 2004, a group called the Civilian Space eXploration Team flew a 21ft rocket with a solid fuel motor to 72 miles high (116km) from a launch site in Nevada.