BERLIN (AP) — Plans to replace Berlin's three small airports with a shiny new one have hit a fresh bump, after campaigners collected enough signatures to force a referendum on keeping a second site open.

Officials said Tuesday that more than 200,000 people have signed a petition demanding that Tegel airport in the northwest of the capital remain in operation.

Tegel was meant to be closed six months after Berlin's new airport began service. But the opening of the new Berlin Brandenburg Airport, or BER, to the south of the capital has been delayed repeatedly since 2011 due to technical problems.

The Tempelhof airport in the center of the city was shuttered in 2008 and is now a recreation ground. The third airport, Schoenefeld, will become part of BER, if it ever opens.