John Boyd and his "acolytes", fellow officers and contractors within the military, tried to circumvent the Pentagon's corrupt and bloated procurement practices. Throughout the 60s and 70s, the Air Force had a fascination with bigger, faster, more complex, and ultimately, more costly jet fighters. These fighters, despite their advanced technology, were ultimately cannon fodder for the more nimble (albeit older and cheaper) MiGs of the North Vietnamese Air Force.
Unfortunately, there was little incentive to change. Many generals in the Air Force were under severe pressure to increase the Air Force's budget, even to the point of buying weapons systems that the Air Force didn't need. Other Air Force generals felt pressure to make aircraft that were increasingly pricey or complex (such as the F-14 and F-111, for example), because these same companies were offering them jobs after their retirement from the military.
John Boyd and his acolytes developed the ultra-nimble and inexpensive F-16 as a result, and it grew into one of the greatest fighters in the world today. Boyd's acolytes also had a little program to develop an air to ground aircraft to destroy tanks. The Air Force felt that an expensive jet fighter would do the trick, while Boyd's acolytes designed a beast of an aircraft to destroy tanks up close: the A-10. Reviled by the Air Force, but beloved by troops everywhere, the A-10 has, in several clashes, taken a punishment from ground fire and still returned safely. It even has two confirmed air to air kills.
With that said, let's look at modern day options for close air support. On one end of the spectrum, we have the possibility that the Marines might resurrect the OV-10 Bronco. An old, propellor-driven aircraft, it has the ability to loiter at low speeds and altitudes for an extended period of time, and drop machine gun fire or bombs on its target. And they're cheap, proven, and relatively simple aircraft--perfect for counter-insurgency.
On the other end of the spectrum, we have the ultra-expensive F-35 Joint Strike Fighter. While sexy and stealthy, it'll be in development for at least another 10 years, and it has already run into extreme cost overruns. Maybe it's time to just axe the program and look for an unmanned vehicle? I don't know, you decide...