Gate squadrons at Bien Hoa were redesignated the 1st Air Commando Squadron (Composite) comprising two strike sections, one of 10 B-26s and 2 RB-26s and the other of 13 T-28s, in addition support squadrons operated 6 C-47s and 4 psychological warfare U-10s. Also on 8 July the 34th Tactical Group was established at the base, taking control of the 19th Tactical Air Support Squadron and the 34th Air Base Squadron. In December 1963 U-2 reconnaissance aircraft operating from the base conducted surveillance missions over Laos and North Vietnam. In early 1964 the USAF and RVNAF were only able to provide half of all requested air support. On 11 February a B-26 operating from Eglin Air Force Base lost a wing in flight and this led to the grounding of all B-26s in South Vietnam. With the loss of the B-26s CINCPAC and Military Assistance Command, Vietnam (MACV) proposed that they be replaced by B-57B Canberra tactical bombers operating under Farm Gate procedures with RVNAF markings and joint USAF/RVNAF crews. At the end of March 48 B-57s flew from Yokota Air Base in Japan to Clark Air Base in the Philippines. On 8 April the remaining B-26s at Bien Hoa flew to Clark Air Base for scrapping. On 24 March a T-28 lost a wing during a bombing run near Sóc Trăng Airfield killing both crewmen and on 9 April another T-28 lost a wing during a strafing run and crashed. Two officials from North American Aviation, the manufacturers of the T-28, visited Bien Hoa and reviewed these losses and advised that the T-28 wasn't designed for the stresses it was being subjected to as a close air support aircraft. As a result, 5 older T-28s were retired and 9 newer aircraft were borrowed by the RVNAF and operational restrictions imposed. Despite this augmentation, accidents and aircraft transfers meant that by late May the 1st Air Commando Squadron had only 8 T-28s left but these were retired on 30 May and replaced by more capable A-1E Skyraiders. B-57 Canberras Following the Gulf of Tonkin incident on 4 August 1964, the Joint Chiefs of Staff began a buildup of U.S. airpower in South Vietnam and 36 B-57B Canberras of the 8th and 13th Bombardment Squadrons at Clark Air Base were ordered to Bien Hoa. As the B-57s approached Bien Hoa on the evening of 5 August one crashed on approach and two