Experts say to consider using tracking websites and apps such as FlightAware to determine whether an airplane is flying in your area.
The White House says many of the sightings are manned aircraft, not drones, operating lawfully.
John Duesler, president of the Pennsylvania Drone Association, said witnesses may be confused about what they are seeing, especially in the dark, and noted it's hard to know the size of the drones or how close they might be.
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"There are certainly big drones, such as agricultural drones, but typically they are not the type you see flying around in urban or suburban spaces," Duesler said Thursday.
Duesler said the drones - and those flying them - likely cannot evade detection.
"They will leave a radio frequency footprint, they all leave a signature," he said. "We will find out what kind of drones they were, who was flying them and where they were flying them."
It is possible that some people may be mistaking general aviation, commercial or military aircraft for drones.
"Drone activity can sometimes be mistaken for general aviation aircraft, such as planes or smaller helicopters, due to several overlapping characteristics," according to the DHS, including "advanced capabilities that allow them to mimic the flight patterns of helicopters or small planes, such as hovering or making rapid directional changes."
How can you tell the difference between a drone and a plane (or other aircraft)?
Most drones are not allowed to fly at night unless they are equipped with anti-collision lights that are visible for at least 3 miles.
Drones have four lights, as do most airplanes flying at night. Drones have lights usually in a tight square pattern, while planes will have lights on the nose and tail and both wings.
Drones also have a unique sound, much like the buzzing of a lawn mower, which can help distinguish between the two.
Can someone shoot down, capture or disable a drone?
Drones generally can't be shot down or captured, for both legal and safety reasons, according to the DHS.
Shooting down a drone can pose safety risks to people and property on the ground. Debris from a downed drone can cause injury or damage, especially in populated areas.
Additionally, the small size and maneuverability of drones make them difficult targets, even if there should be a reason to shoot them down. And while "non-kinetic methods such as jamming or hacking can be used" to disable drones, "they require sophisticated technology and expertise," the DHS says.
It's also not a good idea to shoot them down yourself. Doing so in New Jersey, for example, is illegal and violates federal law, since drones are regulated by the FAA.
According to the DHS, any person who shoots down a drone could be fined up to $250,000 and sentenced to up to 20 years in prison.
State and local authorities also have little to no say legally regarding drone activity, since drones are FAA regulated.
What should you do if you see a drone?
The DHS recommends that anyone who sees what they consider to be suspicious drone activity should report it to their local police.
If you live in New Jersey, you can also report it to the New Jersey Office of Homeland Security and Preparedness Counter-Threat Watch Unit at 866-4-SAFE-NJ (1-866-472-3365) or tips@njohsp.gov.