By Victoria Bryan
BERLIN (Reuters) - It's squat, ungainly and showing its age, but Berlin's Tegel airport is still defying retirement.
Built in the 1970s, the concrete hexagonal hub should have shut down years ago, but embarrassing delays to the city's new international airport have forced its owners to resort to stop-gap measures to keep it going.
Originally meant to serve around 6 million passengers when the main terminal building opened in 1974, Tegel now handles over 20 million a year, and the only way it can take more is if airlines use larger planes.
A lack of investment over the last few years while awaiting the opening of the new Berlin Brandenburg airport means Tegel is now bursting at the seams.
Its concrete architecture contrasts sharply with the gleaming steel and glass structures favored by modern hubs in London, Frankfurt and Paris. Long queues for security checks and restrooms are commonplace.
But many still appreciate Tegel because it is just 8 km (5 miles) from the city center and a public transport ticket to get there costs only 2.70 euros ($3.06).
"The last time I was here was 2002, and nothing much has changed since then," said Simon Wilson, a 55-year old product manager flying back to London after a business trip. Despite standing in a long line for the security check, he said he'd take a small airport like Tegel over a large one any day.
Tegel dates back to 1948, when an airport was built in just 90 days to support the Berlin Airlift, a huge Western operation to ship in supplies and thwart a Soviet blockade of West Berlin.
It was meant to close down around 2012, replaced by a new international hub to the southeast of Berlin next to the existing Schoenefeld airport.
But building problems have repeatedly delayed the new opening. In 2012, it had to be called off just three weeks before airlines were due to move in.
Questions have already been raised over the new target date in the second half of 2017 after one of the contractors declared insolvency over the summer.
KEEP TEGEL OPEN?
To keep Tegel running smoothly until the new airport opens, its government owners are investing a further 19 million euros ($21.5 million) in 2015 and 2016.
The funds are being used for, among other things, a new anti-skid coating on the south runway, improved bathroom facilities, and replacement of a rusted 40-year-old water tank for the sprinkler system.
Airport officials say the latest investment should suffice until Berlin Brandenburg is opened. But some feel Tegel should be allowed to keep going, rather than being shut down.
Fans note the new airport will have a capacity of 27 million, fewer than the 28 million passengers who used Tegel and Schoenefeld last year, and that getting building permission for an additional runway is unlikely in the short term.
The association Tegel Bleibt Offen -- "Keep Tegel Open" -- is trying to gather enough signatures to force a local vote on saving it.
Michael Kromarek, who chairs the association, said Berlin should have more than one airport, like other capitals, and that Tegel should be retained to serve around 10 million passengers a year, mainly on short-haul flights.
"It's a part of Berlin, it's part of its history and Berliners love it," he said.
Berliners have already lost one airport -- Tempelhof, the massive Nazi-built edifice in the center of the city, famed for its role in the Airlift. Now it is used as a vast park, beloved by runners, cyclists, in-line skaters and kite-fliers. There are plans to use it for accommodation in the current refugee crisis.
"Berliners have practiced saying goodbye with Tempelhof and they've learnt how to live without it. Life goes on," said Burkhard Kieker, head of tourism agency Visit Berlin.
(Editing by Mark Trevelyan)