article_snippet.sent: The pictures have since gone viral with internet user suggesting Mysterious white lights were either police helicopters, an optical illusion or an alien aircraft .
article_snippet.sent: Tens of thousands of people have speculated on what the UFO could be, suggesting everything from police or emergence services helicopters, to a kind of optical illusion or even an alien craft.
article_snippet.sent: One YouTube user, Perkoff, believed it was time travelers.
article_snippet.sent: He wrote: 'Most UFOs are not aliens like a lot of people think.
article_snippet.sent: Most UFOs are in fact time machines from the future.
article_snippet.sent: The reason you see so many UFOs at historic events is because people from the future want to come back in time and witness history.
article_snippet.sent: A lot of these UFOs are filled with students and are just going on a futuristic version of a field trip.'
article_snippet.sent: Drones and planes don't disappear like that.'
article_snippet.sent: One YouTube user wrote: 'For me, chances are it's a drone.'
article_snippet.sent: While Francisco Javier Segurasaid: 'It's a airplane, come on!