SAN FRANCISCO — A computer security researcher on his way to give a talk about computer security vulnerabilities at a major conference was told he couldn't fly on United Airlines Saturday, due to comments he'd made on Twitter.

Chris Roberts, of One World Labs in Denver, was on his way to San Francisco for the RSA security conference when he was told by United Airlines that he wouldn't be allowed to board his plane.

"Roberts was told to expect a letter explaining the reasons for not being allowed to travel on United," his lawyers at the Electronic Frontier Foundation, a cyber rights group in San Francisco, posted on Saturday.

Roberts was able to get a flight on another airline and finally arrived in San Francisco late Saturday, said Elaine Hayoz, a One World Labs spokeswoman.

United made the decision not to allow Roberts to fly on United "because he had made public statements about having manipulated airfare equipment and aircraft systems," said Rahsaan Johnson, United Airlines spokesman.

"That's something we just can't have," he said.

Not only are such manipulations a violation of United's policies but, "it's not something we want our inflight crews and customers to deal with," Johnson said.

Although some stories have reported that Roberts got through security and to his flight's gate before he was told he could not board, Johnson said he was actually notified several hours prior to that.