New York Police Department (NYPD) confirmed that the five-foot-long part was discovered by building surveyors between two buildings on the site where a mosque and community center has been proposed three streets away from Ground Zero.
The part bears a "Boeing" stamp, followed by a series of numbers.
Police spokesman Paul Browne said the NYPD had secured the location and would treat it as a crime scene.
More top news
World Number 4 Murray has won their previous five encounters, but Karlovic tops the tournament's aces leaderboard so far.
The Britain's Got Talent judge was accused of singing the national anthem in an American accent and getting the words wrong.
Greece's controversial Finance Minister Yanis Varoufakis has released a defiant statement of resignation entitled 'Minister no more!'