(CNN) - The grand opening of Berlin Brandenburg Airport Willy Brandt was slated to take place in June 2012, and the aviation world was ready and waiting.
Thousands of volunteers had been conducting trial runs in the weeks leading up to the big day.
The media were preparing to provide around-the-clock coverage of the event, which would have the German Chancellor Angela Merkel and numerous other VIPs among its guests.
Lufthansa was even bringing one of its newly acquired Airbus A380s for the inaugural flight to Frankfurt.
But then the unexpected happened -- the inauguration of Germany's new architectural jewel had to be called off at the very last moment due to "technical issues."
Fast forward nearly six years, and the airport remains closed.
Not a single regular commercial flight has used the state-of-the-art terminal and no official date for the inauguration has yet been provided.
The construction of Berlin Brandenburg Airport continues to be an unmitigated fiasco, made all the more striking by the fact that it's taken place in a country known for its engineering prowess.
How it all started
After the Berlin Wall fell in 1989, it became clear in the early 1990s that the capital of the newly unified Germany was in need of a modern international airport. Planning began.
Berlin's three airports, a legacy of the city's troubled 20th-century history, were already showing their age and limitations as the world entered an era of dramatic air traffic growth.
Tempelhof, designated as an airport back in 1923, was the oldest of Berlin's airports, but despite its impressive architecture and historical significance, it closed in 2008.
This left only former East Berlin airport Schönefeld, a favorite among low-cost airlines, and Tegel, the city's main international airport by de facto.
However both airports were designed during the Cold War years and are ill-prepared to handle present-day passenger fluxes. As a result, plans were made to build a new airport on a greenfield site adjacent to Schönefeld Airport -- with construction beginning in 2006 -- and then close down the other two.
It seems this was easier said than done.
What went wrong?
Let's go back for a moment to that eventful day in May 2012, when the airport's entry into service was postponed indefinitely.
A faulty fire-protection system design has taken most of the blame. The system devised proved to be extremely complex.
It envisaged that, in the event of a fire, smoke would be pumped downwards, below the terminal's structure, instead of upwards through the ceiling as per the natural flow of hot air.
But this was hardly the only issue. As time went by, multiple other problems were found such as wiring that overheated, escalators that were too short and serious structural faults in the ceiling, to name just a few.
Ultimately the construction work was found to have fallen short of regulatory requirements, meaning many elements had to be started from scratch.
As if technical issues weren't enough, the project has been plagued by other challenges including allegations of corruption, the demise of several key contractors and a number of legal disputes around the financing of the project.
It's estimated that more than $7 billion has already been sunk into the new airport.
Political and bureaucratic obstacles may have added to the mess.
With two different German federal states involved in the project, the airport became a wrangling ground for politicians at all levels.
"There was never a central management installed to oversee and properly monitor the project as a whole. So this created an environment where no one knew what the real situation was anymore," says Andreas Spaeth, a German aviation industry analyst and author.
"It is still very difficult to properly and realistically assess the state of construction progress and remaining items, hence the reluctance of anyone stating any new opening date now."
The delayed entry into service is creating a whole new set of issues for German authorities to address, namely the future of Tegel Airport, which continues to operate as Berlin's main international hub.
Tegel was expected to close down as soon as Brandenburg went into service, but it's been soldiering on all these years.
The original plan called for the site to be used for a variety of operations, including an innovation and business park.
But this is now under question as local residents voted to keep the airport open in a referendum held on September 24.
And yet, even if the engineering issues are finally resolved, doubts of another nature linger about the longer-term prospects of the airport: Will Berlin ever become the major air center it aspires to be?
Although the city has become a magnet for all sorts of technology-driven and creative industries, it remains the only European capital that's poorer than the rest of its country.
There's a growing demand for air travel, but this is mostly for point-to-point services, predominantly served by low-cost airlines such as Easyjet and Ryanair. Prospects for higher-yield long-haul traffic remain slim.
In this context, the recent bankruptcy of local carrier Air Berlin is an undeniable setback, even if Lufthansa steps in to partly fill the gap, with its new five-weekly direct service between the German capital and New York.
Is the end in sight?
According to Spaeth, the problem may be structural.
"The expectation that Berlin would be able to establish itself as an international and even intercontinental aviation hub was always utterly unrealistic," he says.
"There are far too many established and better equipped hubs already, and one main drawback is that the spending power of the population of Berlin is still very low.
"As there is also a very small local business travel market, especially for long-haul, no airline would be able to turn Berlin as a mega hub into a viable business case. There is simply not enough premium-class traffic demand to and from Berlin."
Perhaps the new airport will be ready just in time to take advantage of the new wave of low cost long-haul carriers that are currently emerging and carve, this way, a market niche for itself.
The German newspaper Tagesspiegel recently reported that Brandenburg might not open until 2021, after a recent inspection identified a range of ongoing problems.
In the meantime, the closest it's come to a regular day of operations was August 2016, as some 24 commercial flights had the chance to use Berlin Brandenburg's runways (though not the terminal) while police deactivated unexploded World War II ordnance at Tegel.