Defense Project Budget Overruns: GAO Acquisitions Data
The US Government Accountability Office produces the most detailed open dataset on defense programme cost growth. In its 2025 assessment, GAO found that combined cost estimates for 30 continuing major programmes rose $49.3 billion in a single year, with the Sentinel ICBM alone driving $36 billion (73%) of that increase.
$49.3B
one-year rise in combined cost estimates, 30 continuing MDAPs (GAO 2025)
$36B
Sentinel ICBM’s share (73%) of that one-year increase
106
costliest weapon programmes assessed, ~$2.4T planned investment
~12 yrs
avg time to initial capability, up 18 months in 2025
Headline overrun examples from GAO assessments
| Programme | Service | Cost growth vs original | Source year |
|---|---|---|---|
| F-35 Joint Strike Fighter | Joint | +108% | GAO-25 |
| Sentinel ICBM (formerly GBSD) | USAF | +81% | GAO-25, Nunn-McCurdy critical breach |
| Columbia-class submarine | USN | +12% | GAO-23 |
| Ford-class aircraft carrier (CVN-78) | USN | +23% | GAO-22 |
| Littoral Combat Ship | USN | +108% | GAO-15 |
| KC-46A Pegasus tanker | USAF | +33% | GAO-23 |
| V-22 Osprey | USMC | +186% | GAO historical |
Cost growth measured against original acquisition baselines, in then-year dollars from GAO Annual Assessments of Weapon Programmes.
Why defense programmes overrun
- Concurrency: Building production units while design and testing are ongoing. The F-35 is the canonical example of concurrency-driven rework.
- Requirements churn: 10-15 year programmes survive multiple administrations, doctrines, and threat assessments. The requirements baseline shifts.
- Optimism bias in original estimates: Programme advocates have an incentive to under-estimate to secure approval. This is the strategic-misrepresentation pattern Flyvbjerg identified for civilian megaprojects.
- Sole-source supply chain: Specialist subsystems often have one or two qualified suppliers. Cost competition is structurally limited.
- Nunn-McCurdy thresholds: US law requires re-certification at 15% / 25% cost growth. Programmes near these thresholds have an incentive to re-baseline rather than admit overrun, which then resets the clock.
Sources and how to cite
US Government Accountability Office (2025). Weapon Systems Annual Assessment: DOD Leaders Should Ensure That Newer Programs Are Structured for Speed and Innovation. GAO-25-107569 (23rd annual assessment, 11 June 2025).
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