The operation to keep the E-4B Nightwatch, the 'Doomsday Plane', in the air

Although the US Air Force is well known for its fighter jets and bombers, one of its most important aircraft is not even armed.

E-4B Nightwatch: this is the inside of the 'Doomsday Plane' of the US Air Force
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Outwardly, the E-4B Nightwatch closely resembles the famous "Air Force One", the aircraft that transports the President of the United States on his trips, as both are based on the same commercial airliner: the Boeing 747. However, the E-4B Nightwatch has a critical function: to serve as an airborne command and communications post in dire situations, such as a nuclear war, which is why this model is popularly known as the "Doomsday Plane".

In 2022, we saw this aircraft inside. Remember that the USAF has four E-4Bs to transport the president and other US civilian and military leaders in case of war. These aircraft are slated to be replaced by the E-4C Survivable Airborne Operations Center (SAOC), a model based on the Boeing 747-8I. Of course, the E-4B wouldn't make sense if it couldn't stay airborne for long periods.

The E-4B has a range of 11,500 km, but that's not enough. To extend its flight time, the USAF has aerial refueling aircraft, including the veteran KC-135 Stratotanker, a model that first flew in 1956 and is based on the Boeing 367-80, the prototype that later gave rise to the famous Boeing 707 commercial airliner. The always interesting YouTube channel Fly By Wire Aviation (which I recommend you subscribe to) has published a video today showing and explaining this complex aerial refueling maneuver (the video is in Spanish; you can activate automatic English subtitles in the player's bottom bar):

Like the vast majority of USAF aircraft, the E-4B is only compatible with the in-flight refueling system known as the "flying boom," developed by Boeing in the late 1940s. This system consists of a deployable boom on the tail of the tanker aircraft, which connects to a receptacle on the receiving aircraft. It is a complicated and dangerous operation, as both aircraft must be synchronized to fly at the same speed.

The flying boom is a system that allows for faster refueling than its alternative, the hose and drogue system, which is used by the U.S. Navy and Marine Corps, as well as other allied countries (including Spain). The flying boom system allows for the transfer of 1,200 gallons (4,542 liters) of fuel per minute, compared to 420 gallons (1,589 liters) per minute for the hose and drogue system.

According to its 2025 Almanac, the USAF currently has a fleet of 504 tanker aircraft: 325 KC-135Rs, 51 KC-135Ts, 89 KC-46A Pegasus, and 39 HC-130J Combat King IIs, the latter equipped with the drogue system for refueling helicopters. These aircraft are of strategic importance to the United States, as they allow for the deployment of other U.S. aircraft anywhere in the world. Their role became evident in the US attack on Iran on June 21, 2025, allowing the B-2 Spirit bombers that carried out the operation to fly nonstop from the US to their target.

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Main photo: U.S. Air Force. An E-4B during an in-flight refueling operation with a KC-135R of the 126th Air Refueling Squadron of the Wisconsin Air National Guard on May 15, 2024.