The US Navy's 'Doomsday plane' took off from Oklahoma Monday and circled parts of Nebraska during a mysterious mission.

The craft, named Boeing E-6B Mercury, left Tinker Air Force Base around 9am ET and soared around Omaha where Offutt Air Base is located.

Offutt Air Force Base is a nuclear command, control and communications base that supports national leadership and warfighters.

Mercury supplies command and control for the US Strategic Command, the Secretary of Defense and the President.

The plane also provides orders to carry out nuclear strikes when necessary.

Flight tracking data shows Mercury made three circles around Omaha before backtracking and returning to the Oklahoma base about seven hours later.

The US Navy has 16 Mercury planes, which are grounded at Tinker Air Force Base and are operated by the Fleet Air Reconnaissance Squadron 3.

The plane has taken several trips out of Oklahoma this past month, with some going to Louisiana, Kansas and California.

AirNav Radar, a flight tracker, captured the plane’s path as it circled and weaved in the skies over Nebraska.

The flight tracker spotted three other Mercury planes in the skies on Monday as well.

One of the planes did a smaller trip, circling outside Tulsa and returning to base one hour later.

Another flew south toward Dallas and the last Mercury was spotted leaving from Maryland.

That flight also lasted no more than one hour. The purposes of the five Mercury flights are unknown.

The 'Doomsday plane' fleet makes up part of Operation Looking Glass, officially known as the Airborne Command Post, which helps communicate with American nuclear forces if ground-based command centers are destroyed.

According to the squadron, its mission is to allow the President and the Secretary of Defense to directly liaise with US submarines, bombers, and missile silos if there is a nuclear war.

In 2020, two were seen flying along both US coasts that October when President Donald Trump and First Lady Melania Trump announced they tested positive for Covid. This was during Trump's first term as president.

One Boeing E-6B Mercury was spotted along the East Coast near Washington, DC, while the other was observed on the West Coast above Oregon.

Social media was abuzz with theories, with many speculating that it was a warning to enemies of America not to attack while Trump is ill and that the US is still strong.

US Strategic Command told DailyMail.com that the timing was merely a coincidence and that the exercise had been planned.

'I can confirm these flights were pre-planned missions,' spokeswoman Karen Singer said in a statement.

'Any timing to the President’s announcement is purely coincidental.'

The E-6B Mercury, also known as a TACAMO (Take Charge and Move Out), is a Boeing aircraft developed for the US Navy as an airborne communications platform.

Boeing built the fleet, also known as a TACAMO (Take Charge and Move Out), for the Navy between 1989 and 1992.

'The TACAMO airplanes support the Navy's ballistic missile submarine force, providing a vital link to the force from national command authorities,' Boeing's description reads.

'The TACAMO E-6B airplanes are equipped with dual trailing wires that serve as transmitter and antenna, transmitting in the very low frequency spectrum.'

Mercury was built to withstand any large electromagnetic pulse generated by a nuclear disaster. It relies on older analogue technology rather than digital technology, which would be fried by the pulse.

The craft carries special equipment and can communicate with anyone, anywhere in the world, and support analysts and strategists in-flight. The planes can also be refueled in the air.

It was also designed to operate in-flight for a full week without needing to land.

The US has another 'Doomsday plane,' known as the Boeing E-4B plane, that was designed to protect the president and high-ranking government officials from an apocalyptic-level attack.

The Air Force currently operates four E-4B aircraft, with at least one on alert at all times at the Offutt Air Force Base in Omaha, Nebraska.

They are typically used to transport the secretary of defense on overseas travel but are tasked with following Air Force One on the president's trips abroad.

The aircraft have been in operation since the Cold War and provide leaders with a survivable command and control center and the ability to deliver orders to the military in the event of a national emergency.

The E-4B planes have three decks with a command room, conference room, briefing room, team work area, communications room, and designated rest area featuring 18 bunks.

The planes have remained airborne and operational for as long as 35.4 hours in one stint, but they were designed to operate in-flight for a full week without needing to land. The E-4B is also capable of refueling mid-air.