There were several times during the war that the U.S. bombing restrictions of North Vietnamese Airfields were lifted. Many VPAF (NVAF) aircraft were destroyed on the ground, and those that were not, were withdrawn to a sanctuary in Red China. In December 1972, the North Vietnamese air defences exhausted their supply of Surface to Air Missiles trying to down the high flying B-52 raids over the North. The North Vietnamese Air Defense Network was degraded by Electronic Countermeasures (ECM) and other Suppression of Enemy Defenses (SEAD) measures. However, the sheer volume of missiles (mass firings) claimed over 15 of the heavy bombers (B-52)s, during the last weeks of 1972 (Operation Linebacker II).
After the negotiated end of American involvement in early 1973, the No. 919 transport corps (Lữ Đoàn Không Quân 371), was formed; and equipped with fix-winged aircraft, as well as helicopters (rotor-wing) in November.
During the Vietnam War, NVAF used the MiG-17F, PF (J-5); MiG-19 (J-6), MiG-21F-13, PF, PFM and MF fighters.[2] They claimed to have shot down 266 US aircraft, and US claimed to have shot down or destroyed 204 MiGs aircraft and at least six An-2s, of which 196 were confirmed with solid evidence. However, VPAF admits only 154 MiGs were lost through all causes, inculding 131 in air combat [5]). Like that, total kill ratio would be 1:1.3 to 1:2.[6][7] With the number of losses to MiGs confirmed by US (121 aircraft shotdown and 7 damaged[6][7]), the kill ratio turn 1.7:1 against the MiGs, or 1.1:1 even accepting the VPAF's figure of only 131 in air combat.