String of close calls between drones and passenger jets in New York City

NEW YORK -- There is an alert about the potential dangers of drones in the skies over New York, after a string of close calls with passenger jets.

ABC News has learned that in just the past 30 days, there have been 11 incidents.

The latest happened over the weekend.

In two cases, pilots have been forced to take evasive action, out of fear of colliding with the unmanned drone.

The worry is that those small drones could do big damage to jetliners filled with passengers.

"The biggest worry is that one of these drones can be ingested by a jet engine at high power on takeoff, for instance, and shut the engine down," said aviation analyst John Nance.

In a statement, the Federal Aviation Administration told ABC News that in the last 90 days there had been a small "increase" in the number of drone incidents in the New York area.

The FAA said that the uptick in reports might possibly be due to an "increased awareness" and that the agency "encourages" pilots to report these close calls.

The aviation source that ABC News spoke with said that as of Friday, controllers had been ordered to make a specific report each time a drone got close to a jet. A federal official told ABC News that reports had included observations by pilots to actual evasive action.

The FAA said it was considering rules as more and more inexpensive flying aircraft take to the sky.

In July, the FAA said it was looking into reports that a drone had hovered above the observation deck of Seattle's famous Space Needle.

And last year, a drone buzzed over the busy streets of New York, flying past iconic landmarks like the Chrysler building and then crash-landing, nearly hitting pedestrians during the height of rush hour.

"The FAA is going to have to work harder and faster to get these rules written," Nance said.