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Close calls between small drones and passenger planes have been skyrocketing, but no tests have been done to determine what would happen if an unmanned craft was sucked into a jet engine.

The federal government has long required that planes be tested for how well they tolerate the impact of bird strikes, but none of the major jet engine manufacturers has done the same for drone impacts, NBC News has learned.

CFM, GE, Rolls Royce and Pratt & Whitney, which combined account for more than 80 percent of the engines used by the world's commercial planes, all confirmed they had not conducted such tests because the FAA has not mandated such testing.

Connecticut-based Pratt & Whitney said that while it carries out "extensive testing" on its engines, it has not examined drone impact "because the FAA does not require such testing at this time." Rolls Royce also told NBC News that it had done no testing because the FAA had not established a standard.

But with the pilot sightings of drones already double last year's figure, the Federal Aviation Administration is now taking action.

Related: Unauthorized Drone Reports Soaring Into the Clouds, FAA Says

The agency told NBC News on Thursday that it plans to develop testing for the impact of a drone on the plane's control surfaces, windscreen and engines during the next fiscal year, which begins Oct. 1.

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"There's always been concerns between unmanned flight and manned flight collisions. This is a problem that has increased in the last year and we have to do something about it. We have to get data," an FAA spokesperson said.

Foreign objects cause damage to jet engines by entering at high speed and breaking or bending the engine's spinning blades, and strikes can even shut down engines, forcing emergency landings.

In the case of drones, the worry is that the plastic parts and the lithium-ion batteries could damage an engine's rotating parts. The testing could determine if an engine is designed to absorb such a strike without catastrophic consequences.

Greg Feith, a former investigator for the National Transportation Safety Board, said the impact of a drone could depend on the engine's size, with smaller engines like those on the popular Boeing 737 and Airbus A320 possibly more vulnerable to damage.

Feith said it's high time for the testing.

"Look at the amount of incidents last year -- less than one a day -- and then the huge increase in incidents this year," he said. "You could say, in retrospect, they should've checked this."

Birds are regularly sucked into jet engines, with most strikes occurring near airports during takeoff or landing. According to the FAA, 15 percent of strikes, including engine ingestion, cause damage to the aircraft.

Pilot Chesley "Sully" Sullenberger made his famous emergency landing of US Air Flight 1549 in the Hudson River in 2009 after Canada geese caused both of the Airbus A320's CFM-made engines to fail.

The deadliest known bird strike knocked an Eastern Airlines turboprop plane out of the sky in 1960 near Boston, killing 62 passengers. An Ethiopian Airlines jet ingested a flock of pigeons in 1988, and 35 passengers died during a fiery emergency landing.

Manufacturers test engines through computer and physical simulation, using dead birds or lumps of gelatin. They rev the engines to full power and then fire real or simulated birds into the machinery with what's called a "chicken gun."

Though some birds, such as Canada geese, can weigh 20 pounds or more, federal regulations require testing for birds as small as four pounds. Commercially available drones, or UAVs, that have been seen near airports can weigh less than three pounds.

Last month, the Department of Homeland Security said in an internal bulletin that it had tallied more than 500 incidents since 2012 in which drones passed near "critical" sites, including airports.

The annual total of all types of incidents rose dramatically from 2013 to 2014. Pilots' reports of unmanned aircraft this year have already more than doubled all of the reports filed last year, the FAA said — from 238 to more than 650 as of Sunday, Aug. 9.

"The FAA wants to send out a clear message that operating drones around airplanes and helicopters is dangerous and illegal," the agency warned this week.

Just in case you don't get the picture, it added: "Unauthorized operators may be subject to stiff fines and criminal charges, including possible jail time."