Air Force Tests Mk21A Sentinel Reentry Vehicle; First Flight Since June 2024
The rebaseline moved Sentinel away from hard external dependencies that had triggered the mandatory Pentagon review, but the program still faces a critical design review gate in March 2027 before it can enter EMD. If that review surfaces integration issues with the W87-1 warhead or heatshield, the FY27 budget bump ($184M increase) may prove insufficient, forcing a supplemental request or another schedule slip. Watch whether the Air Force achieves the planned environmental flight test in FY27 without further program restructuring.
Sentinel's rebaseline in late 2025 decoupled the program from external schedules and introduced an alternate flight test strategy; this October test confirms the Air Force is executing that revised plan and moving toward a critical design review by March 2027.
Lockheed Martin received $996 million in October 2023 and an additional $453 million modification in November 2025 to complete Mk21A development, with the FY27 budget request jumping $184 million to $540 million as integration and test activities accelerate. The Mk21A's heatshield was successfully tested in June 2024; Lockheed was integrating the arming and fuzing subsystem as of February 2026, putting the program on track for planned heatshield and W87-1 environmental flight tests in FY26-27.
Does the October 9 test meet the revised schedule milestones embedded in the November 2025 contract modification, or does the Air Force anticipate further delays before Milestone B authorization for engineering and manufacturing development?
Fault Lines
Strategic intelligence, synthesized daily — with a public track record. Every call graded against what actually happened.