(CNN) — An airline passenger got an amazing surprise when he looked out the window.
Ilya Katsman was on board a Virgin Australia flight from Perth to Adelaide in Australia, when he noticed a spectacular cloud formation, made up of rows and rows of perfectly aligned clouds.
"It was very strange to see, roughly about 20 lines, and it took about 10 or so minutes to fly over," Katsman told CNN.
The rare formation is known as "morning glory clouds," CNN meteorologist Brandon Miller explained.
"The low, horizontal clouds form as a wave travels through the atmosphere and encounters layers of air with different temperatures and humidity levels," he said. "If these layers are at just the right combination of temperature and humidity, they can form clouds as the air rises at the waves' crests -- and no clouds in between, where the air is sinking."
This explains why the clouds look like "breaking waves approaching a shoreline," Miller said.
"Flying above the clouds has never looked this good," wrote Virgin Atlantic, which also shared the incredible photo on Twitter.