In the last 30 days, there have been 10 incidents in which drones have gotten close to passenger jetliners in the New York area, and in some cases, even forced evasive action by pilots, according to a senior aviation official.

The 11th instance occurred in the last 48 hours, the official said.

In two of those cases, the source told ABC News, the pilots turned their aircraft away, worried about a possible collision with the unmanned drone.

Related: Drone almost hits passenger jet. Related: US issues alert about drones and passenger planes.

The worry: 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 today, 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.

ABC News' David Kerley contributed to this report.