In 2016, the Federal Aviation Administration shook up the drone industry by requiring that drone pilots obtain a license if they want to operate commercially.

After years of preparation and debate leading up to the licensing rules, it doesn’t seem that the FAA is aggressively using them to crack down on commercial pilots operating illegally. So far, the FAA has caught and punished only one drone pilot for operating a drone business without a license, according to documents obtained by MarketWatch through the Freedom of Information Act.

The punishment? A warning notice.

Less than a week after the rules went into effect, Jeffrey Slentz wanted some overhead shots of Kauffman Stadium in Kansas City, Mo., for a rap-music video. Before the Kansas City Royals played a game, Slentz flew his DJI Phantom 3 over the stadium.

Police followed the drone to Slentz as he landed it, and the officer was “pretty upset.”

“He was looking for any way to penalize or arrest me,” Slentz said. “He made several calls to the FBI and the FAA.”

The agitated officer was probably not a fan of the ultimate result: A warning letter arrived a week later and prompted Slentz to go get a drone pilots license. That is the only enforcement action the FAA has taken against unregulated commercial-drone pilots in more than a year and a half since the rules passed, according to the records obtained.

An FAA spokesman said that it is possible the agency may be handling violation allegations via education, not enforcement, which may explain why only four records were returned via MarketWatch’s FOIA request for enforcement data related to the licensing rules, known as Part 107. The other three enforcement actions involved licensed pilots who violated rules in which drones can be operated, according to the records. In all of those instances, the penalty was either a warning letter or the operator had to take a safety course at a local Flight Standards District Office.

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Thomas Wasinski, who runs a small drone business based in Hudson, Ohio called Aerial Agents, posted a video to Facebook in January 2017 in which a drone flies over a local Jeep Wrangler parade. Wasinski told MarketWatch that he suspected people from the Facebook group reported his video to the FAA. The FAA reached out to Wasinski and had him take a safety course.

In another instance, Daniel Carnahan flew a drone over a crowd at the Dogwood Festival at a middle school in Camdenton, Mo., in June 2017. He said he wasn’t entirely sure whether it was legal to fly drones over crowds so his friend, a police officer, contacted the FAA. The FAA contacted him a few days later to clarify that it was illegal, and sent along a warning notice.

Carnahan said that as soon as he became aware of the rules about not flying over people, he landed, packed up and left. He said he is careful to abide by all the FAA regulations and has turned down jobs that would require him to break the rules, such as flying drones at night.

His competition doesn’t always follow the rules, though.

“I know tons of people who fly at night, who operate from a moving vehicle,” Carnahan said.

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The FAA suggests contacting the local Flight Standards Office to report Part 107 violations, but Carnahan said that he has contacted the Kansas City Flight Standards Office three times to report a pilot in his area who he knows is flying in violation of Part 107. That pilot, to his knowledge, has not received any punishment and continues to fly drones.

The lack of enforcement has led licensed commercial pilots to wonder why they made the effort. Many say they know of drone businesses operating in their cities — often their competitors — who don’t have a license.

“It’s annoying that other drone businesses are operating without a license and I have no competitive advantage,” said Flo Minton, a Florida-based photographer who holds a remote pilot certificate with the FAA. “I went through all this trouble to pass the test to get my license, including paying for a study course and the test fee, and it took me weeks to study.”

Minton said she has at least two competitors in the area who shoot aerial photographs for their real-estate business, and neither has an FAA license. The FAA has made its database of certified drone pilots publicly searchable online.

“If you’re not going to enforce it, then why enact a regulation?” she said.

As of Feb. 1, there were 73,157 people with an active remote pilot’s license in the U.S. However, Gartner estimated that nearly 285,000 drones were sold for commercial purposes in the past two calendar years, and Skylogic Research founder Colin Snow said he thinks there are significantly more businesses operating without a license.

“Even if you estimated the number of drones owned by each commercial operator at 1.5 per person, that’s still not even close to the amount of people who have a license,” Snow said.

Snow’s drone-industry research firm recently conducted a survey of 938 drone operators, asking about the biggest issues hindering their business’s growth. Although it wasn’t initially one of the multiple-choice options, 77 people wrote in “unlicensed pilots taking their business away.” Comments revealed that licensed pilots fear that amateurs undercut pricing and fly poorly, giving the industry a bad name.

“The fact that so many people thought to write that in, that’s substantial,” said Snow.

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The FAA announced rules for operating a commercial drone business in June 2016, and they went into effect in late August of that year. Those rules require anyone wanting to operate drones for profit to pass a written exam testing the operator’s aeronautical knowledge. With that comes a test fee of about $150, and pilots must also register, which adds an additional $5.

By getting their license, commercial drone pilots must also agree to fly under FAA rules, such as not flying drones at night, in controlled airspaces (for instance, near airports), over people or beyond the operator’s line of sight, though waivers of exemption are available.

An FAA spokesman said it is up to state and local law enforcement to crack down on rogue drone pilots. The FAA has issued guidance suggesting officers collect evidence of illegal drone flights and immediately notify the nearest FAA Regional Operation Center.

“While the FAA retains the responsibility for enforcing Part 107, we also recognize that state and local law enforcement agencies are often in the best position to deter, detect, immediately investigate, and, as appropriate, pursue enforcement actions to stop unauthorized or unsafe UAS operations,” the spokesman said in a statement.

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Police departments across the country say they largely have no idea how to enforce drone laws, however. A spokeswoman for the Hudson Police Department in Ohio, where Aerial Agents is located, said their police officers do not enforce any drone laws. She added that the only situations in which they would enforce any rules related to drones is if someone were attacking people with it, in which case they would treat the drone as a weapon and would file assault or nuisance charges.

And in the incident at the Dogwood Festival in Missouri, the local police only contacted the FAA because they were unclear what the laws were.

The FAA’s lack of enforcement has been setting up a dilemma for drone businesses: Go through the ordeal of getting a license, or just fly under the radar. Minton’s registration is up for renewal in September, and she feels like the “FAA coerced people like myself who are rule-followers.”

“I’m not the type of person that likes to break the law, so I will end up paying another $150 in September,” she said. “If I don’t renew it, I’d know that I am in violation of the law.”

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Many larger operators in the drone industry generally seem happy that penalties appear to be light under the new rules. The FAA had been issuing multimillion-dollar fines to illegal drone businesses before its Part 107 ruling came out.

“Ultimately, the FAA wants to promote business,” Snow says. “They’re not trying to stifle the growth of the industry.”

An FAA spokesperson added that the agency typically wants to educate, not punish, violators, since there is still a lack of public knowledge about how to legally fly drones.

Slentz said that when he was caught flying without a license, his conversations with the FAA were friendly and nonthreatening.

“They emphasized that these rules were new territory,” Slentz said. “They just wanted to make sure I followed the rules, and they realized I was making a good effort to make amends.”

The FAA warned that anyone who intentionally does not comply with those regulations could be liable for civil penalties in excess of $30,000 per violation. Of course, no one has received any such penalty so far.

-MarketWatch staff writer Max A. Cherney contributed to this article.