If you own a drone, the FAA says you have to register it starting December 21

Flying the friendly blue skies under the watch of the FAA.

You might enjoy flying that new drone around the yard this holiday season, but there's a new string attached.

The Federal Aviation Administration said Monday that US residents must register hobbyist drones by February 19 at its drone registration website. Registration opens December 21 and is free through January 20, the agency said. After that, the FAA will charge $5 for registration.

Accepting the guidance of an advisory panel, the FAA said registration is required for any hobbyist drone weighing between 0.55 pounds and 55 pounds. That weight limit includes even relatively small drones like the $549 Parrot Bebop 2, not just the serious $1,000 hobby-oriented models from companies like DJI.

The FAA's registration rule (PDF) applies only to hobbyist drones. Those used for business purposes are prohibited unless the FAA has granted the business a special exemption. The FAA expects to release rules legalizing business use of drones by mid-2016.

Drones, which are typically camera-equipped quadcopters with four rotors to keep them aloft, have become a new consumer and business phenomenon for those interested in remote-controlled vehicles, aerial photography and even aerial racing. As the aircraft have grown in popularity over the last several years, though, drones have become a concern for the government agency responsible for regulating the nation's airspace. In 2014, the FAA received 238 reports of potentially unsafe drone use. So far in 2015, that figure has already reached 1,133.

So far, though, it's hard to truly judge the drone safety risk, said Michael Sievers, an attorney who co-chairs drone work at law firm Hunton & Williams."The FAA has often cited the significantly increased frequency of pilot reports of UAS sightings. But it is hard to judge how accurately those figures represent a real safety problem," he said. High-profile problems only represent a small portion of flights. "That we've not had a truly catastrophic incident is either a sign of very good fortune or a sign of a manageable risk."

The FAA is prepared to enforce its rule.

"Failure to register an aircraft can result in civil penalties up to $27,500," the rule states. "Criminal penalties for failure to register can include fines of up to $250,000."

When registering, drone owners must provide a name, physical address and email address. Drone owners then must mark their drones with a registration number or register its serial number with the FAA.

The FAA believes the cost to operate the drone registration system will be $56 million through 2020.

US Transportation Secretary Anthony Foxx said registration will improve drone safety.

"Unmanned aircraft enthusiast are aviators, and with that title comes a great deal of responsibility," Foxx said in a statement. "Registration gives us an opportunity to work with these users to operate their unmanned aircraft safely."