The United States Air Force, in collaboration with aerospace company Sierra Nevada Corp., has initiated flight testing for its advanced “doomsday plane.”

The tests for the E-4C Survivable Airborne Operations Control, also referred to as SAOC, are taking place at the Aviation Innovation and Technology Center in Dayton, Ohio, as announced by Sierra Nevada on Wednesday.

Sierra Nevada, also known by its abbreviation SNC, conducted the inaugural flight of the SAOC on August 7, marking a crucial phase in the project’s engineering and manufacturing development stage. Both flight and ground assessments are scheduled to continue until 2026, predominantly in Dayton, Ohio, and Wichita, Kansas, as per the company’s statement.

Designed to function as an airborne command and control hub, the SAOC would be operational under extreme scenarios, such as a nuclear conflict or similar large-scale disasters that incapacitate traditional military command structures. In such events, the SAOC would enable the president to manage U.S. military operations and communicate commands directly from the aircraft.

In 2024, the Air Force entrusted SNC with a $13 billion contract to construct five SAOC aircraft to replace its outdated fleet of four E-4B Nightwatch planes. Sierra Nevada is slated to complete the project by July 2036.

These flight tests are crucial for Sierra Nevada as they allow the company to mitigate risks early in the development of SAOC by identifying and addressing potential issues before they escalate and cause project delays.

The aircraft are being constructed from the significantly modified Boeing 747-8 models. Sierra Nevada is enhancing these planes to withstand radiation and electromagnetic pulses, in addition to integrating advanced communication antennas, computing systems, and mission-specific equipment.

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The first Boeing 747-8 designated for the SAOC project arrived at Sierra Nevada’s innovation and technology center at Dayton International Airport in June 2024, shortly after the contract was awarded. Since then, three additional 747-8s have been delivered, with the latest arriving in April 2025.

Sierra Nevada is adopting a modular open systems approach and incorporating state-of-the-art secure communication technologies to construct the SAOC.

This SAOC contract represents the largest single agreement in Sierra Nevada’s sixty-year history, and the company anticipates it will pave the way for further significant contracts.

In response to this expansive project, Sierra Nevada has recently increased its infrastructure. In October 2024, the company inaugurated a second hangar at Dayton airport for converting a 747 into an SAOC and commenced construction on two additional hangars. The first of these new hangars is expected to be operational by October 2025.

The existing fleet of E-4Bs, officially known as the National Airborne Operations Center, has surpassed half a century in service and is approaching the end of its operational lifespan.