WASHINGTON -- The federal government has fined Alaska telecommunication company General Communication Inc. $620,500 for failing to register more than 100 cell towers -- several of which were not properly lit to prevent accidents in the air.

GCI is the largest telecom company in Alaska and its systems provide phone, television and Internet service to much of the state, including many rural areas.

GCI actually brought the violations to the Federal Communications Commission in early 2014, after reviewing its property following the 2013 merger between GCI and Alaska Communications System into the Alaska Wireless Network, according to a legal agreement released by the FCC.

Upon reviewing its inventory, "GCI found that various antenna structures located near airports or otherwise requiring registration had not been registered," and several "were not properly lit," violating regulatory requirements, the FCC said. The structures should have been registered before they were constructed, or when the company acquired them, the FCC said.

"Unregistered and unlit towers pose unacceptable risks to air and public safety," said Travis LeBlanc, chief of the FCC's Enforcement Bureau. "It is essential that communications towers are properly registered prior to construction, as well as properly lighted, to ensure that air traffic is aware of tower locations."

The rules apply to towers taller than 200 feet or those that are in the flight path of a nearby airport.

In addition to the fine, the consent agreement requires that GCI review all of its towers over a three-year period to ensure they are compliant with registration, lighting, environmental and historic review rules.

GCI estimates its antenna structures will be in compliance with the rules by April 30, 2016, according to the agreement. The company has already submitted information about the structures to the Federal Aviation Administration for review.

GCI did not respond to a request for comment.