Retired architect Christian Neunert never dreamed he would be taking part in protest rallies for the first time at the age of 71.

Yet on Monday evening, for the fifth week running, he will ignore his long-held view that only grungy tree-huggers take part in demonstrations, and travel with friends from his home in Mainz to Frankfurt airport to demand Europe's third-busiest airport shrink in size.

The noise is never-ending, he told Reuters. It's destroying my life. Every time I go into my garden, all I can hear and see are planes right above.

Neunert is one of tens of thousands of people from towns around Frankfurt who have suddenly found themselves living directly under the flight path of big airliners when the massive airport opened a fourth runway in October.

Banging drums and blowing whistles, a few thousand protesters have been staging regular Monday protests at the airport. Each week they have forced the closure of rows of check-in desks at its biggest terminal.

The group wants the new runway shut down and a night flight ban, that was introduced a few months ago and has hampered cargo operations at Europe's second biggest freight hub, extended.

With a federal court in Leipzig due to rule on the night flights following a hearing on March 13, the high-stakes battle with airport operator Fraport is nearing a climax.

The trend is definitely towards more restrictions, Juergen Buechy, head of travel association DRV told Reuters.

Fraport wants to increase capacity at Frankfurt, which served 56 million passengers in 2011, to help it secure its role as a hub for lucrative long-haul flights to Asia in the face of rising competition from the Middle East.

Dubai's new World Central Airport, for example, says it will be able to serve up to 160 million passengers a year when it reaches full capacity.

Unfortunately for Fraport, people power is on the rise in Germany. Opponents of plans to build a huge rail station in the southwestern city of Stuttgart managed to force a rare referendum on the 4.5 billion euro project late last year.

The anti-expansion movement has also gained ground in Frankfurt. When the new runway, which cost $792 million to build and was 14 years in the planning, was opened in October, only a handful of protesters turned up.

People just didn't realise back then what would happen, said Ingrid Kopp, organiser of the Monday demos. But now they're forced to put protective headphones on their children as they walk to school.

Kopp, who doesn't live under the flight path herself, sees signs that politicians are starting to pay attention to the protesters. Closure of the new runway has become a hot issue in the Frankfurt mayoral election scheduled for March 11.

FLOWERS FROM NAIROBI

The growing swell of opposition to the runway, coupled with the surprise ban on night flights, has left those firms whose existence depends on the airport fearful about the future.

Lufthansa Cargo, the freight unit of the German flagship airline which is based at Frankfurt, says it is bleeding customers after a local court slapped the ban on flights between the hours of 11 p.m. and 5 a.m. local time.

The company is working on a Plan B, which would likely involve lower investment in Frankfurt and a smaller fleet of freighters, should the night flight ban be upheld.

Flower firm Omniflora, which imports an average of 12-15 tonnes of blooms a day, is also facing increased costs.

The ban has made things very difficult for us, Gerhard Ziran, a managing director, told Reuters, explaining how flowers used to arrive on a night flight from Nairobi, before being packaged first thing and sent out to supermarkets.

With the flight arrival now delayed until the afternoon, it's not until the next day that the flowers reach supermarkets.

It's robbed us of flexibility and of course that is a cost factor, Ziran told Reuters. Before, I could call up Nairobi in the afternoon with last-minute changes for the next morning's order. Now we have to do it all a day in advance.

Massdrei, an events agency, says its lifeblood is the airport. It's not just Lufthansa and Fraport who we organise events for, it's all the other companies based in and around the airport, manager Markus Bonkowski told Reuters.

SILENT MAJORITY

Lufthansa, which has been forced to cut costs to combat high oil prices and a downturn in bookings brought on by the European debt crisis, says Frankfurt needs a big airport with night flights if it is to compete with the fast-growing carriers of the Middle East, especially on routes to Asia.

Businesses in Britain are using a similar argument to urge the UK government to re-examine the possibility of a third runway at Heathrow.

Lufthansa, Fraport and smaller airline Condor, have organised their own pro-airport movement with the slogan Ja zu FRA!

Their aim is to highlight the economic benefits of the airport and stand up for what they describe as a silent majority of people who want it to thrive.

The airport and the region belong together, Fraport Chief executive Stefan Schulte said at a rally on Thursday in Frankfurt's picturesque Roemerberg square.

With 71,000 employees, Frankfurt airport boasts the largest concentration of employees at a single site in the region.

Fraport says expanding the airport would secure those jobs and create thousands more. It points to accounting firm KPMG, which moved its European headquarters to the airport's new Squaire development from London.

In the meantime, Fraport and Lufthansa hope to placate residents with a bigger package of noise reduction measures, including higher flight paths, extra soundproofing for windows and offers to buy up homes under the flight path.

Moving is not an option for me, Neunert said as he picked up his banner, vowing to carry on fighting until the runway is closed.

(Reporting by Victoria Bryan; Additional reporting by Maria Sheahan and Reuters TV; Editing by Noah Barkin and Paul Casciato)