32 aircraft retaliatory attack against a VC base area, claiming to have killed 500 VC. On 2 December 1964 the equipment for the conversion of two 1st Air Commando Squadron C-47s into FC-47 gunships arrived at Bien Hoa. The first FC-47 was ready for testing on 11 December and the second on 15 December. The FC-47s began daytime patrols on 15 December with their first engagement on 21 December killing 21 VC. The first night mission took place on the night of 23/4 December. On 19 February 1965 the Bien Hoa-based B-57Bs mission conducted the USAF's first combat mission bombing VC bases in Phước Tuy Province, in contrast to the preceding Farm Gate missions which were ostensibly conducted by the RVNAF, though in reality carried out by the USAF). This strike was, incidentally, the first time that live ordnance had been delivered against an enemy in combat from a USAF jet bomber. The B-57s conducted further strikes from 21 to 24 February and on 24 February USAF units rescued an ARVN unit under attack in the Mang Yang Pass. On 9 March 1965 the Joint Chiefs of Staff formally approved the use of USAF aircraft for offensive operations in South Vietnam, ending the advisory era. From 3 to 6 May 1965 USAF transport aircraft deployed the 173rd Airborne Brigade from Okinawa to Bien Hoa to secure the airbase and surrounding areas and the port of Vũng Tàu. 1965 Bien Hoa Disaster The use of the B-57s in combat continued to increase as the VC stepped up their attacks on ARVN outposts throughout South Vietnam and the jets were also used on Operation Barrel Roll missions over Laos. On the morning of 16 May 1965, 4 loaded B-57s were awaiting takeoff at the base for a Barrel Roll mission, when a U.S. Navy F-8 Crusader made an emergency landing and was being inspected on the ramp. The lead B-57 suddenly exploded and burst into flames causing a chain reaction of explosions destroying other aircraft, fuel and pre-armed ordnance. The explosions destroyed 10 B-57s, 2 A-1Es and the Navy F-8, killed 28 Americans and 6 Vietnamese and wounded more than 100 more and damaged 25 RVNAF A-1s in what was described as one of the "worst disasters in Air Force history". Among the dead was 34-year-old USAF Major Robert G. Bell, who in 1959 had been one of the 32 finalists for