Researcher denied flight after tweet poking United Airlines security vulnerabilities

SAN FRANCISCO (KGO) -- A security researcher scheduled to speak at a conference in San Francisco this week was denied travel on United Airlines after he suggested on Twitter that onboard aircraft systems could be compromised.

Researcher Chris Roberts was travelling to a computer security conference when United Airlines wouldn't let him on the plane. Roberts was detained by authorities last week for joking he could deploy the oxygen masks.

Roberts founded a security firm whose job is to find vulnerabilities in computer systems before their exploited by hackers.

A United spokesman said Roberts was denied boarding for making "claims regarding manipulating aircraft systems" but said the systems couldn't be accessed the way Roberts described.

The FBI seized Chris Roberts of One World Labs equipment last week.

After flying with another airline Roberts made it to San Francisco Saturday night.

Roberts says it's his job to find weaknesses with airplanes and other vehicles that use electronic systems, but United Airlines says assertions about equipment tampering go too far.

"I'm looking at the entertainment system and going 'I know that this can still be breached. Why isn't it fixed several years after we've had the conversations?'" Roberts said.

Roberts took to Twitter to reveal his frustrations and recently gave interviews regarding his research into airplane vulnerability.

San Francisco-based Electronic Frontier Foundation is representing Roberts. "His job is to make these systems safer. Keeping a security researcher off of a flight for a joke post on Twitter doesn't make the flight safer and in fact, it makes airline security worse in general," attorney Nate Cardoza said.

United Airlines released a statement regarding the flight denial and claims of system vulnerability. "Given Mr. Roberts' claim that he has manipulated aircraft systems while inflight, a clear violation of United policy, we've decided it's in the best interest of our customers and crew members that he not be allowed to fly United. Notwithstanding his attempts, we are confident our flight control systems could not be accessed through techniques he described."

The Associated Press contributed to this story.