A baffling video showing the moment a suspected state-of-the-art spy plane "exploded" over Area 51 has been labelled the best ever evidence that the US government is testing alien technology.

Today marks the date of the "Storm Area 51" viral phenomenon, which has seen millions of people sign up to the FB event to raid the secretive base in Nevada.

But while it is highly unlikely anyone will get close to the base today – the military has even warned they will shoot whoever tries – there has been increased speculation over what is inside the facility.

Conspiracy theorists have long claimed it could house alien technology and even extraterrestrial lifeforms.