The incident has remained unexplained for the past 52 years. But now, a British UFO researcher is proposing a new explanation for Arnold's experience. According to James Easton, what Arnold saw was a flock of pelicans--American White Pelicans, to be exact.

Arnold reportedly saw nine unusual objects that "fluttered and sailed." Initially, he thought they were geese, but dismissed that theory because he thought they were going too fast for birds. Arnold then reportedly decided the objects--which he thought were travelling at at least 1,000 miles an hour--must be a new type of military jet.

While looking into the mystery, Easton contacted an Internet discussion group frequented by Pacific Northwest bird watchers. Members of this group suggested that the size and flight characteristics of the American White Pelican could account for Arnold's observations.

This species of pelican is the largest bird in North America, with a wingspan that can extend to 10 feet or more. Because of their size, the pelicans' underbellies can reflect a lot of light, Easton reports. Easton says his theory has been validated by Peter Kingsmill, the director general of the Redberry Pelican Project Foundation, a conservation group in Canada.

Easton also says he has found a July 12, 1947 newspaper article from the New Westminster British Columbian in which a Northwest Airlines pilot suggests that flocks of pelicans could explain a number of sightings in the Pacific Northwest.