USAF Skyraider units were originally tasked to serve as quasi-training units for the fledgling VNAF. Equipped only with the two-seat models of the Skyraider, American pilots were required to have VNAF 'observers' in the aircraft for every mission. Eventually, this arrangement was changed as enough Vietnamese pilots were trained to man their own squadrons, while USAF squadrons were tasked with close support for US ground forces. Eventually, no fewer than four USAF and seven VNAF Skyraider units saw service in Vietnam. Additionally, one A-1 training squadron flew from Hurlburt Field, Florida, throughout the Vietnam War era. In the ten years that this squadron was active, nearly 1000 USAF and 300 VNAF pilots were trained in the Skyraider. While the core mission of all Skyraider squadrons was Close Air Support (CAS), other missions were accomplished at various times. Among these were Search and Rescue (SAR), night interdiction on the Ho Chi Minh trail, helicopter escort and special forces support to name but a few. Each of these missions took full advantage of the Skyraider's ability to deliver a variety of munitions in close proximity to friendly forces while inflicting heavy casualties on enemy forces