The claims were outlined in a newly released FBI affidavit, which says that Denver computer security expert Chris Roberts told investigators that he not only hacked into in-flight entertainment systems 15 to 20 times but also at one point "caused one of the airplane engines to climb resulting in a lateral or sideways movement of the plane."
According to affidavit, Roberts said that as a passenger he broke into the plane's entertainment system through boxes under the seats.
Law enforcement sources told ABC News there is no evidence that a hacker could gain control of an airliner in the way that Roberts indicated he did.
"While we will not comment on specific allegations, there is no credible information to suggest an airplane's flight control system can be accessed or manipulated from its in-flight entertainment system," a senior law enforcement official said. "Nevertheless, attempting to tamper with the flight control systems of aircraft is illegal and any such attempts will be taken seriously by law enforcement."
ABC News aviation consultant and former Marine Corps pilot Steve Ganyard said that is a possibility and is something the government has said is a problem.
"Nobody can take control of the airplane right now," Ganyard said. "I think somebody can insert bad data. They can spoof and fool the crew. They can say that they are in one place when they're really in another. They can do all sorts of things that could potentially be dangerous. But at this point, we don't have any reason to suggest that somebody can take over the airplane and fly it into a mountainside."
Last month, while traveling on United from Denver, Roberts tweeted about the airplane's system that caused the FBI to be alarmed.
After the plane landed in Syracuse, N.Y., FBI agents immediately met him at the airport, seizing more than a dozen electronic items.
According to the affidavit, agents later found that the seat electronic box on that plane "showed signs of tampering in the location where Roberts had been seated."
Roberts declined to speak with ABC News today but spoke to Fox after last month about hacking into a plane's Wi-Fi.
"It is definitely difficult," he said. "It takes a lot of work. It takes a lot of research and you have to be on quite a number of flights."
Roberts tweeted tonight, "Over last 5 years my only interest has been to improve aircraft security."
Federal sources tell ABC News they believe it is extremely unlikely that someone could hack a plane's control system while in the air.
United Airlines also said tonight that the company is confident Roberts' claims are unfounded.