OLYMPIA — Washington Gov. Jay Inslee has signed a bill requiring wind-power companies to install aircraft-activated lights on wind turbines so blinking lights don’t light up Eastern Washington skies all night.

Inslee vetoed a section authorizing counties to regulate lights. The section was confusing because the bill requires companies to install lights approved by the Federal Aviation Administration, Inslee said.

The bill’s prime sponsor, Rep. April Connors, R-Kennewick, said the partial veto didn’t weaken the legislation’s main point.

“I still feel like we accomplished what we wanted to do, which was turn off the lights,” she said.

Washington becomes one of a handful of states to require wind-power companies to apply for permission from the FAA to install aircraft-detection lighting systems.

If an airplane flies near wind turbines, the lights come on. Currently, lights stay on all night. A proposal by Scout Clean Energy to erect 244 turbines within view of Kennewick heightened concerns about light pollution.

House Bill 1173 will require new wind installations to apply to install aircraft-detection lights. Already operating wind facilities have until 2028 to apply.

If the FAA approves an application, wind-power companies will have two years to install the aircraft-detection lights. If FAA denies an application, the turbines will have lights that are constantly on.

The FAA reviews applications case-by-case. Terrain can interfere with signals and keep aircraft-detection lights from working, according to the FAA.

Connors’ bill passed the Democratic-controlled House and Senate almost unanimously. The bill, however, was opposed by renewable energy groups that testified it should not apply to existing wind turbines.

Aircraft-detection lights would be an unanticipated expense for developers, according to Renewable Northwest.

The opposition made Connors and co-sponsor Rep. Mark Klicker, R-Walla Walla, nervous, Connors said.

“We were worried the whole thing was going to be vetoed,” she said. “I was pleased to only lose that (local government) section.”

The vetoed section stated that county commissioners could adopt ordinances that “included specifications for aviation obstruction light-mitigation technology systems.”

The section wasn’t intended to stop projects, just give counties a say in what type of lights were installed, Connors said. The section did not give counties the power to reject wind projects that couldn’t get FAA approval for aircraft-detection lights.

In a veto message, Inslee said the bill was clearer without the section. The legislation plainly states wind-energy facilities must apply to the FAA to install aircraft-detection lights, according to the governor.

North Dakota was the first state to require wind turbines to have aircraft-detection lights if approved by the FAA. That law passed in 2017. Kansas and Colorado have passed similar laws.

Aircraft-detection lighting systems cost $1.25 million to $2 million to install, according to a presentation to Kansas lawmakers by DeTect Inc., a Florida company.

The systems must be checked at least once every 24 hours and able to detect an airplane at least 3.5 miles from turbines and at least 1,000 feet above turbines, according to FAA regulations.

Washington has 24 wind-energy facilities operating and 12 more under construction or seeking permits, according to the Department of Ecology.

Western Washington Democrats embraced the bill. It seemed more personal for Eastern Washington Republicans. Connors said the first time she saw lights on windmills at night she thought of space aliens.

At a hearing, Republican Rep. Alex Ybarra asked if the bill would apply to the flashing lights he can see from his home in Quincy.