Gogo and others that provide Wi-Fi aboard aircraft must follow the same wiretap provisions that require telecoms and terrestrial ISPs to assist U.S. law enforcement and the NSA in tracking users when so ordered. But they may be doing more than the law requires.

According to a letter Gogo submitted to the Federal Communications Commission, the company voluntarily exceeded the requirements of the Communications Assistance for Law Enforcement Act, or CALEA, by adding capabilities to its service at the request of law enforcement. The revelation alarms civil liberties groups, which say companies should not be cutting deals with the government that may enhance the ability to monitor or track users.

“CALEA itself is a massive infringement on user’s rights,” says Peter Eckersley of the Electronic Frontier Foundation. “Having ISP’s [now] that say that CALEA isn’t enough, we’re going to be even more intrusive in what we collect on people is, honestly, scandalous.”