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The U.S. Air Force and Sierra Nevada Corp. have started flight tests of the next-generation E-4C Survivable Airborne Operations Control (SAOC), or the “doomsday plane,” with the first flight in Dayton, Ohio.

Sierra Nevada said the program has now entered its engineering and manufacturing development phase, with flight and ground testing scheduled to continue into 2026 in both Dayton, Ohio, and Wichita, Kansas. The tests are designed to identify and resolve problems early in the process to prevent costly delays.

The SAOC will serve as an airborne command-and-control center, designed for use in the most catastrophic circumstances. If ground-based command centers were destroyed or disrupted in a nuclear war or other widespread disaster, the aircraft would provide the U.S. president with the ability to direct military forces and relay orders securely from the air.

This program replaces the current fleet of E-4B Nightwatch planes, which have served as America’s “doomsday planes” since the 1970s. The E-4B aircraft, officially designated as the National Airborne Operations Center, is more than 50 years old and nearing the end of its operational life.

In 2024, the Air Force awarded Sierra Nevada a $13 billion contract to build five SAOC aircraft by July 2036. This marks the largest single contract in the company’s six-decade history. An Air Force spokesperson said at the time, “The development of this critical national security weapon system ensures the department’s nuclear command, control, and communications capability is operationally relevant and secure for decades to come.”

The program received an initial $59 million in research, development, test, and evaluation funding to begin work immediately. In addition to building the aircraft, Sierra Nevada is responsible for providing ground support systems, training for aircrew and mission crews, as well as test and sustainment system integration laboratories.

Modified Boeing 747-8 Airframes

The new planes are based on heavily modified Boeing 747-8 aircraft. The airframes are being hardened to withstand radiation and electromagnetic pulses and fitted with advanced communication antennas, secure computers, and mission systems.

The first 747-8 designated for conversion arrived at Sierra Nevada’s Dayton facility in June 2024, just weeks after the contract was signed. Three more aircraft have since followed, with the most recent delivery in April 2025.

Sierra Nevada is using a modular open systems approach to ensure the aircraft can integrate evolving secure communication and planning technologies over the decades ahead.

Expansion in Dayton

To support the SAOC program, Sierra Nevada has expanded its operations in Dayton. In October 2024, the company opened a second hangar to convert 747s into SAOCs at Dayton International Airport and began construction on two more hangars. The first of these additional facilities is expected to be completed and operational by October 2025.

The current E-4B fleet consists of four aircraft, with at least one always on standby for emergency deployment. Beyond their role as presidential command centers, the planes are also used to transport the U.S. Secretary of Defense.

The E-4B, built on the Boeing 747-200 airframe, was engineered to withstand nuclear blasts and electromagnetic interference. However, maintaining the aircraft has become increasingly difficult and expensive due to outdated parts and aging systems. The Air Force expects the fleet to retire in the early 2030s.

Strategic Importance

While many technical details of the SAOC remain classified, defense experts emphasize its role as a crucial element of U.S. nuclear command, control, and communications (NC3). The aircraft ensures that U.S. leadership can continue to operate under the most extreme circumstances, preserving deterrence and continuity of government.

The Pentagon has highlighted that the program includes not just the construction of aircraft but also the development of associated support systems to maintain long-term readiness.

With flight testing underway, the Air Force and Sierra Nevada are moving to validate the aircraft’s performance before full-scale production begins. The program is expected to span more than a decade, with final delivery scheduled for 2036.

For Sierra Nevada, the deal represents both a milestone and an opportunity, as the company positions itself for future large-scale defense contracts.