The World Wildlife Fund (WWF) announced on Thursday that more Americans are expected to mark the Earth Hour by turning off lights.

Saturday will be the third annual Earth Hour observance, which is sponsored by the WWF.

Last year, more than 80 million people in the United States and nearly one billion worldwide turned off their lights as part of the event, according to the WWF.

Among the landmarks that went dark as part of the event were the Empire State Building, Las Vegas Strip, Seattle Space Needle, Great Pyramids of Giza and St. Peter's Basilica in Vatican City, the WWF said.

Earth Hour is designed to encourage energy conservation and call for worldwide leaders to address climate change.

In conjunction with this year's observance, the pylons near the Los Angeles International Airport (LAX) will be dimmed, LAX officials said.

The illuminated pylons that dot the entranceway to LAX will glow solid green for one hour, then will go dark during Earth Hour, which lasts from 8:30 to 9:30 p.m.

The LAX Gateway pylons were first lit in August 2000. They went dark about five years later as more energy-efficient LED fixtures were installed, consuming 75 percent less electricity than the previous system that had 736 lamps, airport officials said.