Sierra Nevada’s first test flight of the Survivable Airborne Operations Center marks a major step in replacing the aging E-4B “Nightwatch” fleet introduced in the 1970s.
The E-4C Survivable Airborne Operations Center (SAOC), the U.S. Air Force’s replacement for the aging E-4B “Nightwatch” fleet, has entered flight testing. Prime contractor Sierra Nevada Corporation (SNC) announced on Sep. 3, 2025, that the first test flight took place on Aug. 7, beginning a multi-year campaign to validate the aircraft ahead of the full modifications.
The SAOC program is one of the most critical elements of the Air Force’s Nuclear Command, Control, and Communications (NC3) modernization effort, designed to provide survivable airborne command and control for national leadership in the event of a crisis or nuclear exchange. Similarly to the E-4B, the new SAOC will be a specialized variant of a commercial derivative aircraft, the Boeing 747-8I.
First Flight and Test Campaign
SNC confirmed that the initial flight occurred at its Dayton, Ohio facility, where the company is hosting four Boeing 747-8I airframes purchased from Korean Air for conversion into the future E-4C fleet. According to the company, both flight and ground testing will continue into 2026 at sites in Dayton and Wichita, Kansas, in order to establish the technical design baseline before extensive modifications begin.
“Accomplishing these test activities early in the developmental program was a distinguishing aspect of SNC’s innovative approach to manage risk and avoid problems from arising later in the schedule,” the company said.
The early test campaign is intended to validate engineering assumptions and reduce risk ahead of the complex work required to harden the 747-8 airframes against nuclear and electromagnetic threats, while integrating secure communications and other mission systems.
A $13 Billion Contract
The Air Force awarded SNC a $13 billion engineering and manufacturing development contract in April 2024 for the SAOC program. The deal covers development, modification, production aircraft, associated ground systems, and interim support, with work scheduled to continue through 2036.
SNC’s selection came after Boeing withdrew from the competition in late 2023. This also represents one of the largest contracts assigned to the company, which in the past has already worked on the Air Force’s A-29 Super Tucano, M-28 Special Operations aircraft, C-130s, as well as the Army’s Athena ISR program.
The program calls for the delivery of aircraft capable of replacing the current E-4B fleet, which averages more than 50 years of service. Though the Air Force has not confirmed how many aircraft will ultimately be procured, reports suggest a possible fleet of eight to ten aircraft. SNC has already acquired five aircraft for conversion.
From E-4B to E-4C
The existing E-4B Nightwatch aircraft, based on the Boeing 747-200, entered service in the 1970s. Their role as the National Airborne Operations Center (NAOC) has earned them the nickname “Doomsday planes” due to their mission: providing airborne command and control for U.S. leadership in the event of nuclear war or other catastrophic scenarios.
The E-4B is designed to carry the U.S. Secretary of Defense as well as other U.S. top officials and always supports Air Force One’s trips abroad. Over the decades, the E-4B fleet has served as a flying command post, capable of coordinating civil authorities, directing military forces, and transmitting Emergency Action Messages to U.S. strategic forces.
The aircraft are hardened against electromagnetic pulses, equipped with secure satellite communications, and capable of operating independently of ground infrastructure for extended periods. That’s why this highly-modified Boeing 747 does not feature modern glass cockpit but old fashioned, analogue-style avionics are more resilient to EMPs.
With the E-4B’s age and growing maintenance challenges, the Air Force has prioritized their replacement. The new E-4C aircraft, built on Boeing’s 747-8 platform, will incorporate modern open-architecture systems, advanced protection against nuclear and electronic attack, air-to-air refueling, and modular mission systems that can be rapidly upgraded.
Industrial Team and Infrastructure
Since being awarded the contract, SNC has rapidly expanded its infrastructure to support the SAOC program. The company has established a growing hub at its Aviation Innovation and Technology Center (AITC) in Dayton, Ohio, adding new hangars to handle the scale of work required.
In April 2025, SNC announced the arrival of its fourth 747-8I aircraft to Dayton. While these four aircraft are already undergoing modification, there are no details about the fifth aircraft.
While SNC is the Prime Contractor, the SAOC team brings together several major aerospace industry partners. Collins Aerospace, GE Aerospace, Greenpoint Technologies, Lockheed Martin Skunk Works, Wichita State University’s National Institute for Aviation Research (NIAR), and Rolls-Royce are all supporting various aspects of design, engineering, propulsion, and mission systems integration, according to SNC.
Strategic Role and Future Outlook
The Pentagon emphasizes that the survivability of airborne command centers like the E-4C is essential for maintaining deterrence. By ensuring U.S. leadership can command forces and manage crises even if ground-based facilities are destroyed, the SAOC strengthens the nation’s command and control capabilities.
The Air Force currently operates four E-4B Nightwatch aircraft. Four would also be the minimum number of E-4Cs required to maintain round-the-clock availability, with one aircraft typically airborne every 12 hours and another on five-minute alert, based on the USAF fact sheet.
Delivery of the full E-4C fleet is scheduled to be complete by 2036. In the meantime, SNC will continue the test and development campaign, progressing toward full-scale modification of the 747-8I airframes in the coming years.
