A helicopter has crashed onto the fog-shrouded roof of a Manhattan skyscraper, killing the pilot and unnerving a city still scarred by memories of September 11.
The crash on a rainy, grey Monday atop the 54-storey AXA Equitable Center forced office workers to evacuate in one of the city's busiest areas a few blocks north of Times Square.
The pilot was the only person aboard when the chopper plunged into the building and burst into flames, New York City Mayor Bill de Blasio told a news conference.
No injuries, either to people in the building or on the ground, have been reported.
"The helicopter is pretty obliterated at this point. It was obviously a very hard hit," de Blasio said, adding nothing indicated "an act of terrorism".
Nicolas Estevez was standing across the street from the building when a 30 cm piece of metal apparently from the helicopter landed on the footpath just metres away.
The crash, which sent people streaming out of the building within seconds, reminded him of the September 11 plane attacks on the World Trade Center in 2001, Estevez said.
"I saw the explosion and the smoke coming out," he said.
A key mystery in the crash is why the Agusta A109E was flying at all in a rainstorm in tightly controlled airspace above midtown Manhattan.
To enter that vicinity, de Blasio said, the pilot would have needed approval from the air traffic control tower at LaGuardia Airport across the East River in Queens, "and we need to find out if that happened."
The Federal Aviation Administration said "FAA air traffic controllers did not handle" the helicopter's flight but a spokeswoman declined to say whether the aircraft was observing prevailing flight restrictions.
The pilot was identified as Tim McCormack, who was going to land at Linden Airport in New Jersey, said Paul Dudley, the airport's director.
"Tim McCormack is a well-respected, highly trained veteran pilot who also had tremendous local knowledge, having flown in this area for many years," Dudley said in a phone interview. "We're all saddened and shocked."
The chopper took off from a heliport on Manhattan's east side and crash-landed on the building 11 minutes later.
The site is about a kilometre from Trump Tower, where US President Donald Trump maintains an apartment. The area has been under a temporary flight restriction since his election in 2016.