Here's Why The Boeing E4 Doomsday Plane Has That Weird-Looking Hump On Top

There are certain aircraft that we hope are never used in anger. The Boeing E-4B Nightwatch is one of these. Often referred to as the "Doomsday" plane, the highly modified aircraft is a militarized adaptation of a Boeing 747-200. The commercial version of a 747 is already easily recognizable thanks to the "hump" toward the front of the aircraft. The Boeing 747's hump was originally designed to easily allow the plane to be used for cargo, as well as passengers. However, the modified E-4 doomsday version has an extra hump — a hump upon a hump, if you will. But just what is the hump for?

To understand this, we need to take a look at the role of the E-4B. The aircraft is a critical component of the National Military Command System, a command hierarchy that includes the President and the Secretary of Defense. In this role, it acts as a National Airborne Operations Center and is called upon in times of national emergencies. Primarily, this would be in situations where the country is under nuclear attack, but it can also be used in other crises, such as hurricanes or earthquakes. The extra hump that adorns the plane plays a crucial part in this role; it acts as a communication hub that uses super high frequency (SHF) and Milstar satellite communications to maintain worldwide connectivity, even in the worst-case scenarios. 

Apart from the extra hump, the E-4 Doomsday plane looks incredibly similar to its commercial brethren. However, scratch beneath the surface — just a little — and the differences soon become apparent. As noted, the weird-looking hump is there primarily to ensure that communications can continue even if the country is facing a nuclear-weapons threat. This could involve maintaining links with nuclear assets and initiating counterattacks through a protocol known as an Emergency Action Message. This somewhat sinister but necessary role is one of the main reasons the plane has earned its "Doomsday" nickname. 

One of the primary methods it uses to facilitate communication is through the Milstar system, which has since been supplemented with the more capable Advanced Extremely High Frequency (AEHF) program. The satellites are part of the United States Space Force, with the Milstar system designed to be a survivable communication system free from reliance on ground-based relay systems. It was also developed to minimize the risk of communications being intercepted. The first Milstar satellite was launched on February 7, 1994, and the last was on April 8, 2003. This was followed by the launch of the first AEHF satellite in August 2010, with the sixth and final one of the group being launched in March 2020. Keeping in touch with this highly advanced and secure communication system is the main reason for the extra hump on the Boeing E-4B Nightwatch plane. 

Despite all the technology crammed into the plane, the Boeing E-4B Nightwatch is still an aging aircraft. This is why there is a new U.S. Air Force doomsday jet in the works. However, this doesn't diminish the capabilities that have kept the current aircraft relevant despite its five-decade tenure. While much of the technology in the plane is classified, we know a lot about the Doomsday plane based on open sources. Among the features that have enabled its longevity are thermal shielding, protection against nuclear blasts and electromagnetic pulses, and an advanced air-conditioning system to keep its electronics cool. It also has a battle staff room that doubles as a mobile command center. The aircraft can accommodate up to 111 personnel, including the crew, support staff, and select high-level personnel.

To ensure that the country is always protected, at least one of the aircraft is always on standby. Once airborne, the plane can fly for 12 hours without refueling, but it also has mid-air refueling capabilities to keep it flying for longer if required. In total, there are four doomsday planes, although it's normal for only three of them to be available at any given time, with the remaining plane undergoing work or maintenance. All the aircraft are based in Offutt Air Force Base in Nebraska, which is also home to the U.S. Strategic Air Command.