E-4

The E00400 - E-4 Modification Program is a critical line item within the Air Force's Aircraft Procurement budget, specifically focused on the modification of the four E-4B aircraft that serve as the National Airborne Operations Center (NAOC). The overarching goal of this program is to ensure the E-4B fleet continues to provide a survivable, global communications platform for national leadership in times of crisis, in accordance with requirements set forth by Presidential Policy Directive 35 (PPD-35), National Security Presidential Directive 51 (NSPD-51), and Homeland Security Presidential Directive 20 (HSPD-20). The program addresses both capability improvements and reliability and maintainability concerns, with modifications spanning communications, navigation, flight control, and mission equipment.

Survivable Super High Frequency (SSHF) Capability Improvement is a major component of the E00400 line item, aimed at modernizing the E-4B's secure communications systems. This project replaces obsolete elements of the Jam-Resistant Secure Communications (JRSC) system, ensuring continued interoperability as the Defense Satellite Communications System (DSCS) is phased out. The SSHF upgrade is structured in two increments. Increment 1 focuses on Ka-band and modem upgrades, while Increment 2 introduces new modem technology, a common workstation, and Ku-band system enhancements. The acquisition strategy leverages Middle Tier Acquisition pathways and is executed in phases to minimize aircraft downtime. L3Harris is the primary contractor for these upgrades, with installations scheduled through FY2026.

Mobile User Objective System (MUOS) Capability Improvement upgrades the E-4B's Ultra-High Frequency (UHF) radio transmitters to provide secure, duplex voice and data communications, meeting both E-4B Capability Development Document (CDD) and CJCSI 6250.01F requirements. This modification enables switchable operation between legacy and MUOS waveforms, enhancing interoperability with other national command and control centers and aircraft. The program includes component and subsystem upgrades. Raytheon serves as the manufacturer for both new installations and retrofit kits. Research, Development, Test, and Evaluation (RDT&E) funds supported prototype development, while Aircraft Procurement, Air Force (APAF) funds cover installation on the remaining fleet.

Advanced Extremely High Frequency/Presidential National Voice Conferencing (AEHF/PNVC) is another significant modification, installing the Family of Advanced Beyond Line-Of-Sight Terminals (FAB-T) and PNVC systems while removing legacy MILSTAR/SECN equipment. This upgrade is necessary to maintain compliance with evolving presidential directives and to ensure continued connectivity as satellite infrastructure transitions to AEHF networks. The AEHF/PNVC system provides protected wideband satellite communications and supports secure conferencing capabilities for national leadership.

Touchscreen Executive Phone-Airborne (TXP-A) and Crisis Management System (CMS) represent new reliability and capability enhancements for the E-4B fleet. The TXP-A replaces obsolete secure phones used by senior leaders, improving durability and multi-level security. The CMS effort integrates government and commercial off-the-shelf solutions to maintain secure communications and crisis management capabilities, supporting the latest CMS network (CMS-Next). These upgrades are essential to meet PPD-35 requirements and ensure the NAOC remains effective across the full spectrum of crisis scenarios.

Service Bulletins and Low Cost Modifications are funded to maintain FAA airworthiness certification and address ongoing reliability and maintainability issues. Service Bulletins are issued by Boeing and executed at the San Antonio depot, focusing on safety, maintenance, and compliance for the aircraft, engines, and mission equipment. The funding profile is driven by due dates and aircraft availability, ensuring timely completion of required modifications to sustain operational readiness. Funding also supports government travel, advisory services, and research contracts, ensuring the program remains responsive to emerging requirements and technological advancements.