The need for a FAC aircraft that could survive in the skies of North Vietnam as well as the ‘hot’ areas of South Vietnam became apparent as the war progressed. The O-1 and O-2 had been used over the DMZ and into North Vietnam itself but by early 1967 enemy air defences had been greatly improved and the slow propeller-driven aircraft proved too vulnerable. As the F-4 was in heavy demand for strike and CAP roles it was decided to evaluate the two-seat F-100F as a fast FAC aircraft. The project was code named Commando Sabre and the specially selected crews used the radio call sign Misty. The unit was initially designated as Detachment 1 of the 612th TFS and was attached to the 37th TFW at Phu Cat on 28 June 1967. Although the crews were assigned to the 612th, most of the aircraft seemed to have belonged to the 416th TFS. Each crew, both pilots, would alternate flying and observing and controlling the strike fighters. All Misty FAC crews were volunteers with at least 100 combat missions in South Vietnam and 1,000 flying hours. The F-100F was well suited for the role but was in short supply and aircraft had to be borrowed from the other F-100 squadrons. The aircraft carried a belly-mounted panoramic stike camera and the observer also used a hand-held camera to obtain target photographs. The Commando Sabre unit later expanded its role to include RESCAP, artillery spotting, photographic reconnaissance, weather reconnaissance and participating in hunter-killer teams with flights of F-100Ds. Maj ‘Bud’ Day was the first commander of the Commando Sabre unit but within two months of the program starting up he was shot down and captured.