A BOEING 747 used by the US president was escorted over lower Manhattan by an Air Force fighter, causing a brief panic among office workers near the site of the Sept 11 terrorist attacks.

Workers from several office buildings poured out onto the streets before they learned that the flights were innocuous and part of a government photo opportunity.

John Leitner, a floor trader at the New York Mercantile Exchange Building, said about 1,000 people "went into a total panic" and ran out of the building at around 10am after seeing the planes whiz by their building, which is near the World Trade Centre site"

He said the workers gathered along the Hudson River until a security officer with a bullhorn told them it was a planned exercise.

"The Federal Aviation Administration and the presidential airlift group conducted an aerial photo mission," said an Air Force spokeswoman.