Is it a bird? Is it a plane?
No, it's just 160 thrill-seekers diving out of one AMP skyscraper and ziplining across a 125 metre gap at a 45-degree angle to the next skyscraper at Sydney's Circular Quay.
But the adrenalin junkies are not in it just for the perfect Instagram shot, with more than $900,000 raised for 15 Australian charities, including The Brotherhood of St Laurence, Cancer Council NSW and Create Foundation.
Some familiar faces were spotted gliding through the skies on Friday and Saturday during The AMP Foundation Big Zipper, including former Sydney Swans player Michael O'Loughlin and??? 2016 X Factor winner and 2017 Eurovision contestant Isaiah Firebrace???.
Despite the 188-metre drop, Firebrace told Fairfax Media that jumping from the building was easier than standing up and performing in front of thousands of people.
"I was more nervous last week before I went out to sing. The jump was exhilarating and very different to singing because I didn't need to think about anything. I could just enjoy the view, it all went too quickly," he said.
Firebrace took part in aid of Ganbina???, a not-for-profit organisation that aims to empower Aboriginal communities to achieve social and economic equality.
"It provides a lot of support for Indigenous kids transitioning from school to work. I think it's really important to support organisations that are grassroots and really connected to the local community," he said.