A Boeing 747 used by the US President Barack Obama was escorted over lower Manhattan by an Air Force fighter jet on Monday, as part of a government photo opportunity that caused panic among city workers and infuriated New York officials.
Workers from several office buildings poured out onto the streets after seeing the low flying planes pass by near the site of the September 11 attacks.
A witness said workers gathered along the Hudson River until a security officer with a bullhorn told them it was a planned exercise.
An Air Force spokeswoman said the flight involved a VC-25, a Defence Department version of the 747 that is called Air Force One when the president is aboard, and an Air Force F-16 jet fighter. They flew over the upper New York Bay and Newark Bay.
The Federal Aviation Administration (FAA) said it notified city law enforcement about the mission.
However New York Senator Charles Schumer said it was "outrageous" that New Yorkers were not told of the event.
New York City Mayor Michael Bloomberg said the flyover so near the World Trade Centre site showed "poor judgment" and was insensitive.
Bloomberg said he was "furious" that the NYPD and another city agency were notified last week, but did not tell him.
"Why the Defence Department wanted to do a photo-op right around the site of the World Trade Centre catastrophe defies imagination," Bloomberg said during a news conference.
New York Senator, Charles Schumer called the situation "outrageous."
"You don't have to be a genius to realise that to have such a fly-by without warning the public could cause real panic," Schumer said.
The NYPD said the flight was authorised by the FAA with directives to local authorities not to disclose information about it, but to direct all inquiries to the FAA.
A White House official later took responsibility for the photo-op, apologising in a statement. White House military office director Louis Caldera apologised in a statement on Monday for the confusion and disruption.
Caldera said federal officials notified local and state authorities in New York and New Jersey.
Caldera's office provides military support for White House functions, including food service, presidential transportation and medical services.
The office oversees all military operations aboard Air Force One on presidential trips.
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