Project 404 was the code name for a covert United States Air Force advisory mission to Laos during the later years of the Second Indochina War, which would eventually become known in the United States as the Vietnam War. The purpose of Project 404 was to supply the line crew technicians needed to support and train the Royal Laotian Air Force, while Raven Forward Air Controllers were brought in to supply piloting expertise and guidance for running a tactical air force. The two programs together comprised Palace Dog.