Story highlights The presence of the large plane and two tailing helicopters raised eyebrows around the city

Trump has said that he plans to return to his home in New York regularly

New York (CNN) A trio of military aircraft seen flying at low levels over midtown Manhattan last week were conducting surveillance and mapping escape routes as part of a security plan for President-elect Donald Trump, two law enforcement officials told CNN Thursday.

The aircraft, identified as an HC-130 search and rescue plane and two HH-60 Pave Hawk helicopters, were taking photos and surveying rooftops and street layouts for the Secret Service in the case that Trump would have to be removed from the city in an emergency, the law enforcement officials said.

Trump has said that he plans to return to his home in New York regularly after taking office next month. Much of his administration's transition planning has been based at Trump Tower on Fifth Avenue, near one of the busiest intersections in the world.

The presence of the large plane and two tailing helicopters raised eyebrows around the city, where the sight of military craft among the skyscrapers is not normal.

"Why is this plane circulating so low in Manhattan?! It brings back bad memories," Twitter user Erdal Kuyumcu posted.

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