Doomsday fears as plane prepped for nuclear war is seen in the skies over the US
The E-6B mercury is a flying command centre to be used in the event of World War 3
A MYSTERY jet spotted by thousands in the skies over Denver has been identified as a E-6B mercury - a flying command centre used in the event of a nuclear war.
The powerful jet was spotted on Wednesday but multiple military officials failed to identify the plane's origin or even its flight destination sparking panic among some onlookers.
Now the plane has been identified as an E-6B mercury – a US Airforce mobile command centre used to launch nuclear weapons anywhere in the world.
According to the Navy's website, the E-6B is a high-tech and large plane, each of which is equipped with an airborne launch control system that can reliably launch intercontinental ballistic missiles (ICBMs).
It would be called into action if the States was ever dragged into another world war.
Local news began tracking the top secret flight – codenamed IRON99 – as it moved over the Pacific, reports the .
After circling the skies for over an hour it eventually landed at Tinker Airforce base in Oklahoma.
Top officials at nearby Buckley Air Force base added to the plane's mystery when they claimed the aircraft never checked in with its traffic control towers.
Denver International Airport staff also confirmed no such plane came into contact with them.
Although the Navy later said the plane simply was flying from its forwarding base back to home base, a high-ranking federal official who wasn't authorised to speak on the matter said the plane was involved in a classified training mission organised by the Department of Defense.
The training mission reportedly centred around electronic surveillance and involved several agencies which aren't likely to comment on the mission, the source said.
The source said the mission wasn't out of the ordinary despite its size, noting the public isn't usually aware of such training missions.
And top military organisations including The North American Aerospace Defence Command (NORAD) said they couldn’t locate the mysterious flight or even confirm it existed.
The planes from the ground up look a lot like Boeing 707 units because the plane is modelled off the old Boeing product.
Often painted bright white to look nondescript, the planes have more than six hours of loiter time in the air and have a range of just over 7,500 miles.