The chief executive of United Airlines cast doubt Tuesday on claims by a security researcher about hacking the controls of a jetliner from its entertainment system.

"There are clear firewalls between a Wi-Fi system and any kind of control," United president and CEO Jeff Smisek told a US Senate hearing.

Smisek said however the matter was "of great concern to us" and that the carrier was cooperating with an FBI investigation into the matter.

A story circulating in security circles in recent days is based on a claim by researcher Chris Roberts of One World Labs that he briefly took control of a United aircraft from his passenger seat by hacking into the in-flight entertainment network.

An FBI warrant shows the federal law enforcement agency carried out a search of Roberts' computer and other materials after his claim on social media that he was able to take control of certain flight functions on a United flight on April 15 after hacking the entertainment system.

Smisek told the Senate panel of the alleged hacking, "We are unaware of whether or not this is possible (but) the original equipment manufacturers, from at least what I understand, have stated this is not possible today."

But a congressional report last month said hackers could exploit in-flight entertainment systems to fatally sabotage the cockpit electronics of a new generation of airliners connected to the Internet.

In-flight cybersecurity is "an increasingly important issue" that the Federal Aviation Administration (FAA) is just starting to address in earnest, said the audit and investigative arm of the US Congress.

At Tuesday's hearing, FAA chief Michael Huerta said the agency was cooperating with the FBI and examining the potential vulnerabilities.

"We're working closely with the manufacturers to understand how the threat -- how the threat morphs, how it evolves, changes and how do we stay ahead of it by having, as we've always had, many layers of security and control over access to critical systems within the aircraft," he said.

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