A prominent computer security expert was barred from boarding one United flight, removed from another, and detained by the FBI—all apparently over a tweet pointing out how easy United’s security system would be to hack.

Chris Roberts—the founder of security analysis firm One World Labs—tweeted about vulnerabilities on his United flight’s engine-indicating and crew-alert systems (EICAS) last Wednesday.

That same day he was reportedly pulled off a United flight and questioned by the FBI for more than four hours. His lawyers also claim the FBI seized his laptop, iPad, hard drives and other equipment without a warrant.

The FBI reportedly determined Roberts—who was warned not to access flight controls after publicly identifying vulnerabilities in AirBus and Boeing systems—meant no harm.

“I don’t know what the logic is. They’re probably pissed that FOX picked up on it and CNN picked up on it and it’s gotten a lot more media attention,” Roberts tells securityledger.com. “This has been a known issue for 4 or 5 years where a bunch of us has stood up and pounded our chest and said this is an issue…Are they pissed because there are credible threats and we’re giving those credible threats more intelligence, or because we’re standing up and saying ‘there’s a problem,’ or because they can’t get anywhere with this?”

But either way, United isn’t having it: Roberts was reportedly removed from a second flight while en route to a security conference in California. An airline spokesperson tells the AP that the airline feels “confident” about its system but still considers Roberts a threat.

“Given Mr. Roberts’ claims regarding manipulating aircraft systems, we’ve decided it’s in the best interest of our customers and crew members that he not be allowed to fly United,” airline spokesman Rahsaan Johnson told The Associated Press. “However, we are confident our flight control systems could not be accessed through techniques he described.”

Johnson did not respond to a follow-up question Sunday why Roberts would still be a threat if he couldn’t, in fact, compromise United’s control systems.

United tells reporters Roberts should receive a letter in the next two weeks explaining why he’s been barred from the airline.

[image via AP]

Contact the author at gabrielle@gawker.com.