The 12 Most Famous Project Budget Overruns in History

The most famous construction overrun in history. Jorn Utzon won the 1957 competition with a radical design, radical to the point that nobody knew how to build the roof shells. Construction began in 1959, before the structural engineering was solved. The AUD 7M budget was set before the engineering of the roof was understood.

Utzon's relationship with the New South Wales government deteriorated as costs escalated. In 1966 he resigned, and the interior was completed by a different team, meaning the acoustic performance of the concert halls was compromised. Final cost: AUD 102M against an AUD 7M budget, 14.6 times the original. Foundations were laid in 1959 and the building opened in 1973.

Primary failure: Construction started before design was complete. No realistic cost estimate existed. Political pressure to proceed trumped engineering reality.

The Central Artery/Tunnel Project in Boston is the most expensive highway project in US history. Its 1985 estimate was $2.6B (GAO); by May 2007 project officials put the total at $14.798B (Massachusetts State Auditor), about 469% more in nominal terms. A section of tunnel ceiling collapsed in 2006, killing one person.

Key overrun drivers: underground Boston is full of historic utilities, foundations, and contamination that were not fully mapped. Cost-plus contracts gave contractors limited incentive to control costs. A series of design changes was approved without full cost impact assessment. The project also used an unusual delivery model for the time (design-build), which was not yet well understood.

Primary failure: Inadequate site investigation, cost-plus contracts without incentive for cost control, and 25 years of scope additions.

Berlin Brandenburg Airport became Europe's most infamous construction project. It missed its planned October 2011 opening by nine years, opening in October 2020. Budgeted at about EUR 2B when construction began in 2006, it cost EUR 5.9B to build, according to the Berlin Senate in 2022.

The most concrete failure: the fire-protection system could not be approved and had to be redesigned and rebuilt. The supervisory board approved constant design changes without understanding the engineering implications. There was no single, accountable project manager for much of the project's life: responsibility was shared between government shareholders who had political rather than technical expertise.

Primary failure: Governance vacuum, design changes approved by non-engineers, defective systems installed and not caught until late inspection stages.

The UK's high-speed rail project is arguably the most politically contentious infrastructure project in recent British history. The 2010 command paper estimated London to the West Midlands at £15.8B to £17.4B (2009 prices); the full network was put at £37.5B in 2009 prices by later Commons Library and Institute for Government accounts. Phase 2 to Manchester and Leeds was cancelled in October 2023, yet in May 2026 the Department for Transport put the surviving London-Birmingham section alone at £87.7B to £102.7B (a mixed price base: spend to date in cash, remaining work at 2025 prices), with first services expected between 2036 and 2039. See the full HS2 case study.

The National Audit Office identified optimism bias in the original estimates, poor scope definition, and tunnelling cost underestimates as primary drivers. Design choices (high-speed specification requiring elaborate tunnelling through the Chilterns) added billions not reflected in early estimates.

Primary failure: Classic strategic misrepresentation: the estimate was politically constructed to be low enough to secure approval rather than accurately reflecting the engineering reality.

A June 1997 study put the Next Generation Space Telescope, which became James Webb, at $500M with a 2007 launch (US House Science Committee hearing charter, 2011). GAO's 2021 assessment gives a $9.7B life-cycle cost estimate, about 1,830% more. The $500M was a science-community study figure, not an agency baseline: against NASA's 2009 baseline of $4.96B the growth was 95%.

The technical complexity was genuinely unprecedented: a deployable 6.5-metre mirror operating at -233C in deep space, folded to fit inside a rocket, was beyond the engineering state-of-art in 1997. Redesigns, contractor problems and testing failures pushed launch from 2007 to December 2021. The US Government Accountability Office (GAO) flagged the project as high-risk repeatedly.

Primary failure: Technical cause: the original estimate was based on an immature design for technology that did not yet exist. Arguably an acceptable overrun given the scientific returns.