Why spotting this plane in the sky could mean you only have five minutes left to live

I hate to be the bearer of bad news, but if you ever catch this plane whizzing overhead then it may be an indicator of impending doom.

The idea of a doomsday plane sounds like something ripped straight from a low budget apocalypse thriller, but most pieces of fiction usually have a kernel of truth behind them and, given how rocky global politics are at the moment, it shouldn't be too much of a surprise that world leaders have a contingency plan available for the worst case scenario.

So, what exactly is the doomsday plane and what are your chances of imminent doom if you see one?

A Boeing E-4 being refuelled in the 1990s (USAF/Getty Images)

What is the 'doomsday plane' and what does it mean if you see it?

Known as the Boeing E-4 or National Airborne Operations Centre (NAOC), this particular military aircraft is designed with the event of a nuclear war or global catastrophe in mind - hence why you only have about five minutes in the worst case scenario.

Put simply, the plane is a modified aircraft designed to operate as a mobile war room for the President of the United States. The E-4 can also fly for around 12 hours at 600mph and it can also refuel without landing, meaning it can survive in the sky for an entire week.

Sounds pretty dystopian, right?

Originally created back in the 1970s, the Boeing E-4 was designed to offer a cold war president a place to survive a nuclear attack, while also launching retaliatory missiles.

The United States isn't the only nation to have prepared for the worst case scenario either, with Euro News also reporting the existence of a 'Flying Kremlin' designed to give the Russian President (aka Vladimir Putin) the same apocalyptic capabilities.

These bad boys aren't cheap to run either, setting the military back $159,529 (£126,000) per hour to operate and making it the Air Force's most expensive plane.

The Boeing E-4 planes also come with a number of defence mechanisms, such as the ability to withstand electromagnetic pulses and analog flight controls, which mean the aircraft wouldn't be susceptible to cyber attacks.

According to MailOnline, the US has four of these doomsday planes, with one on high alert at all times, and are based at the US Strategic Command, south of Omaha, Nebraska.

CNET also adds that the aircraft are capable of carrying a crew of up to 112 people and are jam packed with high-level communication technology.

Although we're not sure who you'd be talking to if the planet has been wiped out in a nuclear apocalypse.

A rare peak inside the flying nuclear bunker (US Department of Defense/CNBC)

What happens if you spot a 'doomsday plane'?

As scary as the doomsday plane sounds, you shouldn't immediately panic at the sight of one, as they're also sometimes used to transport officials overseas for events and meetings.

But if it really is a harbinger of end times, perhaps it's better to be on Earth rather than circling a destroyed planet for several days before the inevitable happens.