with the active forces being reduced after the end of the vietnam war, a significant number of older c-130a hercules tactical airlifters became available for the air national guard and air force reserve, which allowed the korean war-era c-119 flying boxcars and c-124 globemasters to be retired. however, the total force concept led to pressure to upgrade the reserve forces to front-line aircraft and beginning in 1974, new ling-temco-vought (ltv) a-7d corsair ii ground attack aircraft began to be sent to air national guard units directly from the ltv manufacturing plant in dallas. as a-10 thunderbolt iis began to replace the a-7ds in the regular air force in the mid and late 1970s, additional a-7d aircraft were transferred to the ang. f-4 phantom iis began to be received by the ang in the late 1970s with the f-15a eagle and f-16a fighting falcons coming into the active inventory and ang's f-100 super sabres being retired.