A highly specialized U.S. military aircraft known as a “doomsday plane” was seen flying repeated loops over a major Air Force installation in Nebraska on Monday, just hours before President Donald Trump’s deadline for Iran to accept his proposed agreement was set to run out.

The aircraft, a Boeing E-4B Nightwatch built to safeguard top government officials and maintain command operations during a nuclear conflict, was tracked flying above Offutt Air Force Base, which houses the headquarters of U.S. Strategic Command.

Flight tracking data showed the jet departing Offutt at 10:17 a.m. EST, circling the surrounding area at least six times before eventually returning to the base, according to a report by the Daily Mail.

Such flights often draw attention during periods of heightened geopolitical tension. A similar mission last year attracted notice shortly before the United States joined Israel in a 12-day campaign targeting Iran’s nuclear infrastructure.

Trump has set a Tuesday deadline for Iran to accept his terms, which include reopening the Strait of Hormuz. He has warned that failure to comply would result in U.S. strikes on critical infrastructure, including power stations and bridges.

“The entire country can be taken out in one night, and that night might be tomorrow night,” Trump told reporters at the White House on Monday.

The United States maintains a fleet of four E-4B aircraft, which routinely conduct flights throughout the year to ensure constant operational readiness.

The Nightwatch aircraft functions as a mobile command post for the president, the secretary of defense, and the chairman of the Joint Chiefs of Staff, enabling uninterrupted leadership and communication during crises.

Equipped with multiple levels, the plane includes sleeping quarters with 18 bunks, as well as a briefing space, work areas, a conference room, and a command center, effectively serving as a fully operational “flying Pentagon” in emergency situations.

The aircraft has been specially reinforced to endure extreme threats, including nuclear detonations, electromagnetic pulses, cyberattacks, and other catastrophic scenarios.

Each E-4B can accommodate up to 112 personnel and is capable of traveling distances exceeding 7,000 miles without refueling.

It is also outfitted with advanced shielding and an extensive communications system, including dozens of satellite dishes and antennas housed within its radome, allowing it to maintain contact with virtually any point on the globe.