June 24 marks the anniversary of the event that helped launch America’s modern fascination with unidentified flying objects.

On June 24, 1947, private pilot Kenneth Arnold reported seeing nine bright, unidentified objects flying in formation near Mount Rainier. His account became one of the first UFO sightings to receive widespread national attention in the years following World War II.

Arnold was flying near the mountain when he said the objects moved rapidly across the sky. He described their motion as similar to a saucer skipping across water. News reports interpreted the description as referring to the objects’ shape, helping popularize the phrase “flying saucer.”

The objects were never definitively identified. Arnold initially considered whether they could have been experimental military aircraft, but officials said no test flights were taking place in the area at that time.

The report was followed by a surge of similar sightings across the country and helped establish the public interest in UFOs that would continue for decades. While accounts of unusual objects in the sky existed long before 1947, the Arnold sighting is widely regarded as a starting point for the modern UFO era.