Drone sightings by aircraft pilots have increased approximately five-fold in the past year, according to the Federal Aviation Administration.
The agency said pilots spotted more than 650 drones in the first seven months of 2015, compared to 238 sightings in all of last year.
The FAA released the numbers as part of a plea to the public to keep their unmanned aircrafts away from airports, manned aircraft and wildfires.
“Unauthorized operators may be subject to stiff fines and criminal charges, including possible jail time,” the agency said in a statement when releasing the numbers.
A number of close calls between drones and pilots have been reported recently, and firefighters on the West Coast recently had to temporarily ground flights because of the presence of drones in the area.
As drones become increasingly popular, the agency has launched a public awareness campaign to teach safe flying. But it noted it has also imposed fines for a number of unauthorized flights.
The FAA has recommended that recreational flyers keep their drones within their line of sight and below 400 feet. It has also barred the use of most drones above 55 pounds.
The FAA has proposed regulations for the use of drones for commercial use. Some lawmakers have proposed legislation that would require drones to come equipped with collision-avoidance software as well.