Drones are continuing to take off as Christmas gifts.

This holiday season, shoppers will buy nearly 1.6 million drones, up 31 percent from last year, according to the Consumer Technology Association.

But on Christmas morning, remember this warning: If they weigh more than 0.55 pounds, the high-flying gadgets have to be registered with the Federal Aviation Administration.

A registrant must attach a drone ID number, linked to the owner's name and address, and pay a $5 fee.

"Registration gives us the opportunity to educate these new airspace users before they fly so they know the airspace rules and understand they are accountable to the public for flying responsibly," said FAA Administrator Michael Huerta, in a 2015 press release announcing the registration plan.

These 2015 regulations were tossed out by a federal judge in September, but a December bill signed by President Trump restored them.

The FAA says owners who fail to register drones weighing more than 0.55 pounds will be subject to civil and criminal penalties.

The FAA wants operators to be mindful of where their unmanned aircraft systems are permitted. Since November 2014, the government has received growing reports of unauthorized drone sightings.

Drones are prohibited around airports, major sports stadiums and wildfire fighting operations. Some localities, including Washington, D.C., are "no drone zones," where unmanned aircraft systems are outright prohibited.

"The agency wants to send out a clear message that operating drones around airplanes, helicopters and airports is dangerous and illegal," says the FAA's website. "Unauthorized operators may be subject to stiff fines and criminal charges, including possible jail time."

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