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.^[1] The purpose of the mission 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.

Project 404
Patuxay, was built in Vientiane during the 1960s with USAID funds awarded for building a new airport runway. Humorously renamed the "Vertical Runway" by U.S. mission personnel.
Operational scope	Diplomatic Military Attachés Strategic
Planned by	United States Department of State CIA
Objective	Counterinsurgency Foreign internal defense
Date	1966–1973
Executed by	U.S. Army Attachés U.S. Air Force Attachés Air America
Outcome	North Vietnamese Army and Pathet Lao Conquest of Royal Lao Government 1975

Project 404 began in 1966, as a successor after the completion of Operation White Star, was smaller in scope, and was an adjunct to the various covert ground operations succeeding White Star. Because Laos was ostensibly a neutral party to the conflict between the United States and North Vietnam, the airmen did not wear United States Air Force uniforms, but instead worked in civilian clothing.^[2]