Drone users are facing the possibility of fines up to $27,500 and even jail time if they have not registered their devices with the federal government. 

The Federal Aviation Administration's Feb. 19 deadline for drone registrations, which was set in December, has now passed. 

The agency says "failure to register an aircraft may result in regulatory and criminal sanctions." 

"The FAA may assess civil penalties up to $27,500," the FAA said in a frequently asked questions post on its website. "Criminal penalties include fines of up to $250,000 and/or imprisonment for up to three years." 

The FAA is imposing a $5 fee for registrations, over the objections of drone advocates, but the agency provided refunds people who registered their drones within the first 30 days of the new requirement.

The agency said Monday that 368,472 drones were registered by midnight on Feb. 19, surpassing the number of airplanes that are on record with the federal government. 

FAA Administrator Michael Huerta says he is encouraged by the response to the drone registration rules, which were implemented by the Transportation Department in December after an increase in the number of reported drone sightings by commercial airline pilots. 

"The speed with which we were able to roll this out is a testament to the invaluable input we received from the diverse task force of stakeholders we brought together to work on this issue," he said in a recent speech at a drone policy summit in Washington.

"It’s proof that when government and industry partner, we can innovate, cut through red tape, and use technology to tackle emerging risks."

Drone users have complained about the fees, labeling them a "drone tax." A drone hobbyist in Silver Spring, Md. and a technology group have sued the FAA over the rules, arguing the mandate violates a federal law prohibiting the FAA from regulating recreational drones.

The FAA has defended the legality of the system, saying the agency has the authority to regulate all "aircrafts" that are flown in the U.S. The agency has also defended the drone registration fee is nominal.