Contents

Letter 1

Background 5

DOD Reviewed 36 Weapon Systems in Fiscal Years 2023 and 2024 and Identified 14 with Critical O&S Cost Growth 12

Navy and Army Have Taken Some Actions to Address Critical O&S Cost Growth Identified in Fiscal Years 2021 and 2022, but Army Has Not Fully Implemented a Key Software Update 22

DOD Is Taking Steps to Address Sustainment Review Challenges 28

Conclusions 32

Recommendation for Executive Action 32

Agency Comments and Our Evaluation 32

Appendix I Operating and Support Cost Changes of Weapon Systems Reviewed in Fiscal Year 2023 35

Appendix II Operating and Support Cost Changes of Weapon Systems Reviewed in Fiscal Year 2024 39

Appendix III Detailed Information on the Causes of Critical Operating and Support Cost Growth, by Weapon System for Fiscal Years 2023 and 2024 42

Appendix IV Comments from the Department of Defense 50

Appendix V GAO Contact and Staff Acknowledgments 52