Projects of immense scale and complexity are never easy to execute, so it's little wonder that so many are delivered late and massively over budget. The impacts of the COVID-19 pandemic, runaway inflation, and supply chain issues over the recent years hasn't helped either. 

Read on to discover the staggering costs of some notoriously problematic projects and discover why they're still running so far behind schedule. All dollar amounts in US dollars, unless otherwise stated.

Designed by the world-renowned Zaha Hadid Architects, Mumbai's shiny new international airport was first proposed back in 1997.

The project was eventually given the green light in 2008 but has been marred by conflict, mainly between government departments.

Bitter disagreements over the location, concerns over the ecological impact of the airport that put India's environment and civil aviation ministers at loggerheads, and protests from local villagers are just some of the issues that have delayed the project so far. 

Foundations were finally laid in February 2018 but the phase one completion date of April 2019 that was estimated by Maharashtra chief minister Devendra Fadnavis couldn't be met.

The state had hoped that the airport would be ready to launch its first flight by December 2020. However, construction of the runway hadn't even started by the end of 2019 due to nearby residents' reluctancy to relocate.

Further financial issues have impacted the project's progress, with the original budget of $692 million (£567m) more than tripling to $2.1 billion (£1.7bn). 

The pandemic also put a stop to construction on the site, with the airport's managing director revealing that the megaproject would be delayed again.

In November 2020, Maharashtra chief minister Uddhav Thackeray set a new completion deadline of May 2021 for the first phase. He also warned that further delays wouldn't be tolerated, with the new airport viewed as crucial for securing future investment in India’s largest planned city.

Despite that sense of urgency, the May deadline came... and went. The most recent time frame suggests that the airport's phase one should be fully operational by December 2024, almost three decades after it was first proposed.

Delays aside, the project has seen some modest progress. At the end of June 2022, officials announced that airport would be renamed DB Patil International Airport after Dinkar Balu Patil, the former leader of the Peasants and Workers Party.

With the goal of overhauling the region's railway system, the Stuttgart 21 project in southern Germany has been controversial from the very start.

The megaproject was officially announced in 1994 with an estimated price tag of €2.5 billion ($3.3bn/£2bn), although construction work didn't actually start until 2010.

Unexpected increases in construction expenses and environmental regulations – including the relocation of thousands of lizards in 2017 – have delayed the construction of the massive new train station in Stuttgart, along with several of its tunnels and about 50 miles (80km) of new railway tracks.

The initial completion deadline of 2019 couldn't be met and costs have been spiralling out of control.

In January 2018, rail company Deutsche Bahn approved a financing framework of €8.2 billion ($9.3bn/£7.3bn) for the project, pushing it €5.7 billion ($6bn/£5.3bn) over the original estimate.

The project is now on track to be completed by late 2025, with its cost rising further to €9.15 billion ($10.1bn/£7.7bn) thanks to higher prices and increased geological risks. Some meagre progress has been made, the Wendlingen-Ulm line entering service in late 2022.

The construction of the Hinkley Point C nuclear power plant was approved by the UK government back in 2016.

Located in Somerset, England, it has two accolades to its name: not only is it the first nuclear plant to be built in the UK in more than 20 years but it's also set to be the world's most expensive.

And the budget for this controversial megaproject keeps going up. In 2016 EDF Energy announced the plant would cost £18 billion ($23bn). This price tag has been repeatedly revised, with the most some estimates suggesting it will actually cost £32 billion ($39bn). 

As well as blowing its budget, Hinkley Point C is behind schedule.

The concrete base of the first reactor was completed in June 2019, while the base of the second reactor was completed, on time, in the summer of 2020.

But in a statement released in January 2021, EDF announced that it didn't expect Unit 1 to start generating electricity until June 2026, around six months later than its original target of late 2025.

Some of the construction delays stemmed from the pandemic when work was postponed to enable social distancing. And by May 2022, EDF had pushed the deadline out even further to 2027 saying labour shortages and inflation were now creating issues. 

This April, the contractor started the final offshore works to install massive vertical shafts into the seabed, a celebrated milestone. However, estimates for the power plant's price tag range between £25billion and £26 billion ($31bn-$32bn). 

Construction began on a new reactor at the Flamanville Nuclear Power Plant in northern France in December 2007.

Owner and operator EDF budgeted €3.3 billion ($4.9bn/£2.4bn) for the project and said it would take 54 months (four-and-a-half years) to complete.

Commercial operations were meant to have started in 2012. Yet a plethora of problems ranging from safety concerns to equipment issues have put a major spanner in the works, delaying the project significantly and adding billions to the cost...

An initial decree from the French government stated that fuel loading at the new reactor must be completed within 13 years of the construction work starting in 2007. However, a new decree was published in March 2020 that extended that initial deadline to April 2024. The loading of fuel into the reactor was forecasted to happen by the end of 2022, a deadline missed due to faulty welds and corroded safety valves.

EDF maintains a 2024 deadline is still within reach. However, with complicated repairs on the overdue project, the budget has increased accordingly. The reactor is now expected to cost the French energy firm €13.2 billion ($14.5bn/£11.7bn), marking an increase of nearly €10 billion ($11bn/£9bn).

Plus if the project achieves its latest deadline, it will actually need to shut down shortly afterward to replace a component of the vessel in compliance with French nuclear regulations.

Upon its completion, the Gulf Railway Line will connect the six Gulf Corporation Council (GCC) member states: the United Arab Emirates, Saudi Arabia, Oman, Qatar, Kuwait, and Bahrain.

The total length of the track will be 1,353 miles (2,177km), with each state organising the construction of the project within its own territory.

Plans were originally approved back in 2009 and original estimates suggested the line would cost around $14 billion (£10.5bn) and be operational by 2018.

However, that hasn't been the case.

By 2016, several partner countries had suspended work on their projects due to a lack of funds from the collapse of oil prices in 2014-2015. Dr Sulaiman al-Hamdan, the Minister for Transport in Saudi Arabia at the time, announced that a large portion of the project in his country had been completed. However, conflicting sources suggested that the construction work hadn't even begun...

Investment in railway infrastructure kept going ahead in some areas, though, with the UAE completing a 159-mile (256km) line between Dubai and Abu Dhabi. Then in 2022 the Gulf Railway Line found major momentum with Saudi Arabia confirming it too had built 125 miles (200km) of rail for the project. Other countries have renewed their efforts to restart construction.

The total cost of the project, which is split between the six involved nations, is now tipped to be more than $200 billion (£160bn), more than 14 times the original budget of $14 billion (£10.5bn). 

Located in Georgia, the Vogtle Electric Generating Plant is a nuclear power plant that became operational in the 1980s.

Units 1 and 2 of the plant consist of a pressurised water reactor, steam turbine, and electric generator that collectively generate 2,430 megawatts of electricity. That's comfortably enough to power more than half a million homes. 

In 2006 the site applied to build Units 3 and 4, which would allow it to increase its nuclear capacity. But although the plans were approved back in 2009, progress has so far been slow and expensive.

The new units, which are 60 stories tall, are the first nuclear power plants to be built in the US for more than 30 years.

According to the plans, Unit 3 should have been operational in 2016 and Unit 4 should have followed in 2017.

But Japan's 2011 Fukushima disaster caused progress to stall, with anti-nuclear campaigners filing a lawsuit against the plant due to safety concerns. 

To make matters worse, power company Westinghouse – which was responsible for designing, engineering and managing the megaproject – went bankrupt in 2017.

The work was taken over by Southern Nuclear but delays have followed. Current estimates suggest Unit 3 will be ready by June 2023, with the reactor connecting to the electricity grid for the first time in early April. Unit 4 is in testing and expected to go into service no later than 2024.

The total cost of the project has soared to more than $30 billion (£24bn), easily double the original budget of $14 billion (£10.5bn).

Since the early 1980s, California has been planning to connect the state's largest cities via a high-speed train line.

In a 2008 referendum, voters approved a $9.95 billion (£6.6bn) budget to begin construction of an 800-mile (1,287km) rail link.

With an estimated total cost of $40 billion (£29.4bn), the project promised to take travellers from Los Angeles to San Francisco in just two hours and 40 minutes.

However, the megaproject has been delayed by protests, lawsuits, and planning issues from the outset. Construction on an approximately 200-mile (320km) segment finally began in 2015, almost three years behind schedule.

Project costs had skyrocketed to $77 billion (£62bn) by 2019 when president Trump's administration cancelled a grant worth nearly a billion dollars, which would swiftly be followed by the pandemic – also resulting in cuts to funding. 

Though the election of president Biden has proven to be good news for this megaproject – his administration reinstated the revoked funding – the costs keep mounting.

In 2022 the California High Speed Rail Authority (CHRSA) released a business plan outlining a smaller project of only 500-miles (800km) with a much steeper final cost of $105 billion (£84bn). This year it increased that to $128 billion (£103bn) with no word on when the system will be ready, but with hopes that the initial 200-mile (320km) segment might be in service in 2030-33. 

High Speed 2, better known as HS2, is a high-speed railway line that's currently under construction in the UK.

When finished this 330-mile (530km) railway will connect London to Northern cities, including Manchester and Birmingham.

The plan was originally proposed in 2009, with a route agreed upon the following year. Authorities announced that phase one of the megaproject, which would carry passengers between London and Birmingham in 52 minutes, would be up and running by 2026.

But more than a decade after the plans were first unveiled, work on the £33 billion ($41bn) railway has been derailed... 

The controversial megaproject has been met with fierce opposition due to its environmental impact and eye-watering price tag.

Construction of the railway line will destroy almost 900 properties, 1,000 businesses, and 60 historic woodlands. And although HS2 has been billed as an eco-friendly alternative to cars, carbon modelling has suggested that the project's carbon dioxide emissions could actually exceed any potential savings.

Widespread protests have contributed to HS2's ever-extending timeline, while unforeseen costs have caused the budget to balloon. 

Barely a month after construction officially began in 2020, the cost of the railway had already rocketed to £106 billion ($141bn) and completion dates rescheduled as late as 2040 for phase two. 

A third phase, which would have carried passengers between London and the northern city of Leeds, has been scrapped entirely – with the government hoping to keep the price closer to £96 billion. But that's still nearly three times the original estimate of £33 billion ($41bn).

Construction does continue on the rail project, with the most recent estimates confirming additional delays of at least two more years, and forecasting the initial London to Manchester line won't see service until well into the 2040s. 

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