(Bloomberg) -- Reports of errant drones flouting U.S.regulations including flying too close to passenger airliners andother aircraft surged late last year to an average of fourincidents per day, according to Federal Aviation Administration data.

The 1,200 incident reports in 2015 were more than five times the236 the FAA recorded a year earlier when it first began compilingthe data. By the second half of last year, there were an average offour reports per day, according to figures released Friday by theagency.

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“We have a number of educational initiatives with our governmentand industry partners to teach drone operators how to fly safely,including the drone registry we launched last December,” FAAAdministrator Michael Huerta said in a press release. “Butenforcement goes hand-in-hand with education, and we will takeaction against anyone who operates irresponsibly to the full extentof the law.”

The incidents grew substantially over the same period a yearearlier, even as the FAA began a mandatory registration system forowners of all but the smallest toy drones. There were 93 incidentsin January after the registration system for newly purchased droneswent into place, compared with 26 in January 2015.

Airline crews

While there were no reported collisions in the latest data and mostincidents were sightings with little chance of a mid-air impact,there were numerous instances involving airliners or largeaircraft. In the last two weeks of January alone, at least sevenairline crews said they spotted drones while flying.

On Jan. 30, ExpressJet Airlines Inc. pilots spotted a whitedrone within 300 feet (91 meters) while flying at 19,500 feet(5,944 meters) near Atlanta, according to the FAA. ExpressJet is aregional carrier operating flights for American Airlines GroupInc., Delta Air Lines Inc. and United Continental Holdings Inc.,according to its website.

Other close calls involving airliners occurred above Miami,Chicago and Salt Lake City, according to FAA.

The FAA requires that drones fly below 400 feet (122 meters) andsteer clear of other aircraft. It also says drone operators muststay more than five miles from airports unless they get permissionfrom air-traffic controllers.

The agency predicts there will be 2.5 million drones sold this year and annual saleswill climb to 7 million by 2020.

The Academy of Model Aeronautics, which represents hobby dronepilots, urged that the latest figures be viewed with cautionbecause most of the sightings didn’t involve a safety risk.

“A more definitive analysis of the data is needed to separateout the lawful operations from those that pose a true safetyconcern,” the group said in a posting on its website.

Related: FAA urges largest fine yet on drones in crackdownon near misses

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