Marty Kottmeyer's article
The Saucer Error
explains how the very idea of a "flying saucer" is based upon a misunderstanding of what Arnold said he saw. But since people thought that Arnold had said he'd seen a saucer, then by golly, saucers were what they reported seeing! (Article excerpted from
The REALL News,
Volume 1 No. 4.)
James Easton was the first to suggest that what Arnold actually saw was a flock of American White Pelicans, the largest birds in North America.
The late Philip J. Klass suggested that Kenneth Arnold probably saw Meteor Fireballs.