Reference

Paul Harvey, a famous broadcaster, perpetuated the myth that Mary Babnik Brown's hair was used to create the crosshairs in the Norden bombsight during World War II. This story, although widely promoted, was incorrect. Mary Babnik Brown's hair was indeed donated during the war, but it was actually used for weather instruments, not for the Norden bombsight.

You can find more detailed information on Mary Babnik Brown and the perpetuated myth on her Wikipedia page.