Here is another news article for your collection. Although the article is centered on the performance of a helicopter for rescue, there is mention of a person using a signal mirror to attract the flight crew attention.

Below, Anderson saw the aircraft and heard its familiar mechanical whine. But he thought they didn’t see him, so he used a signal mirror to get their attention.

“The helicopter was about 1,500 feet below us and there were other hikers waving at it just to say hello,” he said. “I was afraid the crew would be distracted, so I used a signal mirror to get their attention while I called the Coast Guard again on my cell phone.”
Earth and sky, woods and fields, lakes and rivers, the mountain and the sea, are excellent schoolmasters, and teach some of us more than we can ever learn from books.

John Lubbock