Okay, first let's look at the numbers of combat aircraft in the USAF:
F-16 Fighting Falcon General Dynamics F-16C/D    982
A-10 Thunderbolt II Fairchild Republic A-10C         280
F-15E Strike Eagle McDonnell Douglas F-15E         219
F-15 Eagle McDonnell Douglas F-15C/D                 193
F-22 Raptor General Dynamics F-22A                    186
B-52 Stratofortress Boeing B-52H                           78
B-1 Lancer Rockwell B-1B                                       62
F-35 Lightning II Lockheed Martin F-35A                 47
AC-130 Lockheed & Boeing AC-130U/W/J                27
B-2 Spirit Northrop Grumman B-2A                         20
 
See that? The A-10 is the second most numerous model, third most numerous airframe (since both F-15 variants are on the same frame).
Does that sound like something they're "trying to get rid of"?
Now, I keep hearing the same ignorant, and sometimes idiotic, comments about this, fueled by internet outrage, emotional stories, and instant expertise.
"The Air Force refuses to do CAS for the Army."
Really? In what battle did the Air Force refuse to do this? Please name the event, date and location.
"The Air Force wants to get rid of the only plane that can do CAS."
Really? What do the Army, Marines and Navy use for CAS, since they have no A-10s? What do other NATO allies use?
"The Air Force should be ordered to design a replacement."
You're an idealistic idiot and that's not how that works. The USAF doesn't design craft.  First, it holds a forum to determine needs, which costs money and takes Congressional approval. Then, it takes the needs to Congress, and begs them for money for R&D. Then, it has contractors submit proposals, and has Congress assign money to develop prototypes. Then it tests the prototypes. Then it picks one, begs Congress to bless it, then begs them for money to build it.  Then, Congress blames the cost on the AF, counts the R&D into the production cost, claims the production cost is too high, halves the numbers, complains the per unit cost has doubled, halves it again, complains how expensive new planes are, and cancels the project. And it takes 20 years.
BTW, we DO have such a replacement. It was even designed with the participation of the Navy and Marines. It's called the F-35. Oops.
"The Soldiers love the A-10, so the Air Force should be made to keep it."
Okay, and? Since when does a grunt's personal desires dictate air doctrine? HINT: Never.  Marines liked the battleships for beach support.  The Navy still got rid of them when they got old.
Then we get into really stupid territory.
"The Air Force should just give it to the Marines. They want it."
A: Cite, please, the USMC document stating their interest in this platform.
2) The Marines vastly prefer aircraft that are carrier capable, for forward deployment.  This leads to the response of:
"So just put carrier landing gear on it and make the wings fold."
a} You don't "just" put carrier gear and folding wings on an airframe. It has to be DESIGNED for such. Even if it is
II] that adds a LOT of weight to the frame, typically about double, which reduces your payload, so you wouldn't have an A-10 anymore, and
C. it would cost a CRAPTON of money.
V| how do you think, btw, the Marines do CAS now, if they have no A-10s? Possibly they use other aircraft?
Then we go full retard.
"The Air Force should be made to give it to the Army."
Okay.  So, assuming you revoke the Key West Agreements and give it to the Army, what then?
Hey, Army, that sure is a nice looking plane you have there. Looks GREAT!
Oh, right...the Army doesn't have any fixed wing CAS pilots. I wonder where they'll get those?
Oh, you think USAF pilots will just transfer right over and take the Army's bullshit to fly the plane?  (All branches have bullshit, but they're used to USAF bullshit, and prefer it, or they'd have gone Army in the first place.) Well, SOME Hog drivers will, they love the plane that much. But others will say, "Fuck it, I'll go back to Vipers."
So, the Army will have to get trained pilots. And who will train Army pilots on the A-10? OH, right--USAF pilots. And that will take a year or so.
So, now they have planes and pilots...and where do they fly these planes from? Army FOBs are sorely lacking in runways.
Now, if you were stupid enough to propose this idea, you're probably stupid enough to think some poured concrete and planks makes a runway, and I'm going to laugh in your face.
Where is the Army going to get trained airbase engineers?
So, either beg, borrow, or steal them from the USAF, OR, add enough Army engineers to do the job, AND have the USAF train them in how to build airbases.
Get that? You have to ADD PERSONNEL to the Army to do this. And the USAF isn't going to lose any personnel, which I'll come back to in a bit.
Then, you need jet mechanics, airframe specialists, aircraft electricians, pneumatics-hydraulics specialists, life support equipment, munitions, PMEL and NDI specialists, ground support...
And all those troops need support troops--medics, supply, cooks, etc.
Some can be cross-trained from existing Army fields, but you'll still need more of them.
You're going to build 10 Expeditionary Air Wings for the Army.
And then you're going to give them a single 40 year old airframe that, best case, is going to retire in 13 years, and only does one mission, and the rest of the time, sits there as a target while the support element sits there waiting.
Oh, yeah--more MPs.
I've even heard from Army aviation troops where the Infantrytards wanted to pull them off duty, "park" the helos and just fire them up when needed. If you don't understand why that doesn't work, you probably are the type of person who proposed the idea above, so it would take too long to explain why you're an idiot.
More importantly, there's a very good chance you're in the Army, and have Dunning-Krugered yourself enough to think that operating aircraft is SIMPLER than driving trucks and shooting rifles (Yes, I was in the Army, I know there's more than that, but I'm responding with a like attitude. How does it feel?).  Thanks. You've proven EXACTLY why we have the Key West Agreement and why the Army doesn't get to manage the Air Force.
Now, coming back around--it's ONE craft that does ONE mission. It was the best plane in the world at busting tanks, 40 years ago. It was one of the best at busting bunkers, movements and positions, 40 years ago.  But that's all it does, and it's no longer as awesome and unique as it was.
You see, other aircraft can do those missions. Sometimes they have to overlap, but those craft also do other things, and the A-10 does not. So, the USAF will keep all its existing personnel for its other aircraft.  All you'll have done is driven up Army costs and complexity.
These days, CAS is done by A10s, F16s, F15s, AC130s, B52s, occasionally B1s, but not, as far as I know, by B2s. It's done by Navy and Marine FA-18s, AV-8Bs, EA-6s, Marine and Army AH-60s, AH-64s, AH-1s, and various UAVs. Smart munitions make a lot of difference.
Now, let's look at the F-16. It has this cute trick where, if you try to attack it during its CAS mission, it suddenly goes supersonic, locks onto you, and splashes you with Sidewinder air to air missiles that it pretty much always carries for just such an emergency.
The A-10, in similar circumstances, has this cute trick where it calls for an F-16.
Which means your Army CAS wing would need a USAF fighter wing to cover its ass while it did its mission, assuming a modern enemy with an air force.
And if you're not fighting a modern enemy with an air force, you probably don't need A-10s to blow them up, most of the time.
It was originally designed to bust tanks in the Fulda Gap, when we were outnumbered 25:4.  The plan was to go in slow, low, blow stuff up, take a lot of fire, duct tape back together, take more fire, and hope the aircraft lasted long enough to reduce the tank numbers so the Army could handle what was left.  It wasn't expected to survive, just to die with style.  And "Close" in this case is about 4000 yards. That's what the gun is indexed for.
Forty years later, neither the Russians nor Chinese would let an A-10 get that close. They know what it can do, and they have much better air defense.  You're going to have to send high performance fighters anyway, and stand off and lob missiles. In which case, the fast movers can lob the missiles, and you don't need an A-10.
Oh, sorry, did you say "BRRRRRRRRRT!"?  That's not quite the sound it makes, actually. It's more like a farting dragon. But it also turns out that if you get that close, you don't usually need 30mm to punch holes, and if so, Maverick missiles do it from 20 km away, and if you really think you need to get close, UAVs are cheap and don't risk pilot lives.
Now, are there missions for which the A-10 can't be replaced? Yes, a few. The combination of slow and lots of hardware does have its place (helos require more maintenance, have less loiter time, and smaller payloads).
But, then we come to budget.
The USAF is tasked with some essential but non-combat missions. Heavy strategic airlift, theater airlift, nuclear deterrence, intel and reconnaissance, refueling, transport.  Those all move material and people into and around the war zone, and deter our enemies.
The combat missions roughly break down to interdiction-strike, interception, air superiority, and close air support. Four main categories.
So, hypothetically, if you have four missions, ten planes per mission, you have forty planes.
Then you get told your budget is 35 planes.
The strike craft can do CAS.  The air sup can be equipped to do some, as can the interceptors. But, the CAS craft can't do ANY of the others.  If you have to get rid of 5 birds, it's going to be the ones you can't cross-deploy. It's simple numbers. An F16 is not an ideal CAS platform, but it can and has done it. It can also intercept, strike and maintain air superiority.  An A-10 cannot intercept, cannot do air superiority, and can do strike, but not long range (not quickly enough to matter in most engagements) and not without cover from the others.  There is ONE recorded air-to -air kill by an A-10, of a hovering helicopter. Against any kind of modern fighter, it is steak.
You want to keep the A-10? The USAF needs more budget.  Cut some of those handouts to non-productive people and put that money back into defense (and roads, and schools, and science, but DoD for this argument) and they can fly more missions with more aircraft.
Now, the USAF will continue to fly the A-10 for the next several years. And even when it doesn't, it will cheerfully kill anything the Army paints with a laser or has a JTAC identify. Because blowing shit up is cool.
It was doing that before the A-10 existed, and will do it afterward, and will probably do it better in the future.
But it won't be with the A-10 for long, because even though there are older aircraft, most of them don't take the heavy pounding of low altitude, high-G maneuvers, nor as many sorties.
In the meantime, new gunship packages are being developed to put even more firepower into them. They shoot sideways and poop bombs out the back ramp.  Expect to see a lot of that doing CAS.
Now, the F-35 is almost an air parallel to the M-14 rifle. The M-14 was intended to replace the Garand, the Browning Automatic Rifle, the Thompson, the M3A1 Grease Gun and the M1 Carbine.  In the end, it was a so-so replacement for the Garand at 3X the unit cost, but didn't do anything else worth a damn. It seems no one learned from that history.
The M-14 was a terrible replacement for the BAR, and all hopes had been pinned on it.  It failed.
But we still got rid of the BAR.  It was old, it no longer was as awesome as it had been in WWI, so it went away.
The M-60 was probably a terrible choice to replace the BAR. It was a general purpose machine gun, not an automatic rifle.  But it's what we had.
So the A-10s replacement, if not the F-35, will possibly be some cobbled together C-17 Globemaster with forward firing 105mm howitzers.
