Why Were Low-Flying Military Choppers Darting Between Chicago Skyscrapers?

With the NATO security summit a little more than a month away in Chicago, the city is in high gear preparing for the influx of dignitaries and world leaders. Most recently, Blackhawks and A/MH-6 Little Bird helicopters were seen cruising among the skyscrapers, but officials state that this was part of a routine training in urban environments, unrelated to summit preparations. Still, others speculate it is in fact related to the May 20-21 event.

(Related: Why the change of venue? G-8 Summit now being held at Camp David instead of Chicago)

The local Fox affiliate reports this training exercise "rattled windows" of some downtown offices, not to mention the nerves of witnesses. It also states that some viewers reported men hanging out of the windows with automatic weapons.

According to My Fox Chicago, the city was warned with a press release about the exercise, but it didn't quite prepare residents and workers for what they were going to see:

“It was frightening,” Jessica Hill said. “I was definitely alarmed.”

At least three Blackhawk helicopters flying at time in close order formation - at other times separating fairly widely -- zoomed around office and residential towers for several hours.

“I was pretty amazed,” Felise Llano said, “because they were definitely military.”

Witnesses described three to four very heavily armed men in each chopper. Several said some of the men appeared to be tethered and were at times literally hanging out of the choppers, and looked ready to jump.

Watch the report for more:

My Fox Chicago also points out that the details about some security preparations for the Nato Summit were released by the Secret Service recently, including several terrorist and crowd control measures. The Chicago Sun Times called this list of materials ordered for the event "sensitive but unclassified."

As the city prepares for the event, so do protesters. A march is being organized against the summit with the organizer Andy Thayer calling NATO “the world’s most expansive and dominating military empire in history," and "the key to US military dominance abroad.”