Helicopter tours are a threat to national security.  The New York Post points to some of the reasons.

• The tours fly low and very close to iconic landmarks like the Statue of Liberty and the World Trade Center.

• There is virtually no security at all at the Downtown Manhattan Heliport from which all of the tours take off and land.  Screeners use a wand to scan for weapons, but passengers are not patted down and they are free to carry sharp nonmental objects like pens and pencils.

• The TSA has no involvement whatsoever.  Last-minute walk-ins are welcome.
• There is no barrier between the passengers and pilot.  Passengers have free access to the pilots, making it easy to overpower them.
• The tours fly past hundreds of buildings on both the New York and New Jersey sides of the Hudson River making them easy targets for sharpshooters

“The mayor has the ability to close [the helicopter tours] down entirely.  Increased security concerns in the city, I think, give this issue new urgency.’’  -- Councilman for the Upper West Side, Mark Levine