New Yorkers were mystified by the presence of military aircraft over the city that never sleeps earlier this month. Low flying planes and helicopters circled around parts of the city which has not forgotten how two planes smashed into the World Trade Center on September 11, 2001.

ABC News reported that law enforcement officials revealed that the aircraft were conducting a training exercise on how to safely airlift President-elect Donald Trump out of Manhattan.

The purpose of the exercise was to determine where a helicopter could touch down near Trump Tower to move Trump and others to safety.

Retired Army Maj. Mike Lyons and a military analyst said that the aircraft may also have been looking at surrounding rooftops to determine possible evacuation routes.

"Police and law enforcement have got to be as creative as terrorists could be in recognizing that during 9/11 they weren't able to evacuate anyone from the rooftops," Maj. Lyons said. "The first thing they are likely looking at is a possibility from Trump Tower."