At the Air Force, leaders have set their sights on grounding a plane that’s been a reliable standby for decades. But its defenders won’t give up without a fight.

Defense producer Dan Sagalyn has been tracking the debate.

Kwame Holman narrates this report.

KWAME HOLMAN:A typical day at Martin State Airport on Maryland’s Eastern Shore includes chemical weapons training with the A-10 Warthog.

The National Guard base is one of the homes of an aircraft beloved by ground forces, who see it as their guardian in the sky. Its pilots view infantry on the ground as their primary customer and responsibility. Most combat aircraft shoot down other planes or drop bombs or both. But the Warthog was designed specifically to come in low and attack enemy forces in a mission called close air support.

MAN: North and South, west of the smoke, west of the smoke.

MAN:OK, copy. West of the smoke, I’m looking at danger close now.

KWAME HOLMAN:Oftentimes, the enemy is within yards of friendly forces. This video captures the exchange between a Warthog pilot and a ground controller calling in a strike on Taliban forces in 2006 in Southern Afghanistan.

MAN:Roger. Keep your fire west of the smoke.

MAN:OK. Copy that.

KWAME HOLMAN: Major Chris Cisneros trains Warthog pilots in the Air Force’s 104th Fighter Squadron.

MAJ. CHRIS CISNEROS, Air Force: Close air support is kind of a pickup game, if you will. If a friendly convoy is out, and they have come under fire unexpectedly, you want to talk to the good guys, figure out where they are exactly, and then find where the enemy is and execute from there.

KWAME HOLMAN:The Air Force has about 350 Warthogs. Flying below cloud cover, its pilots can see with their own eyes what they’re attacking. It can loiter over the battlefield, a cockpit protected by a titanium shell and bulletproof glass, making it survivable even when hit by small-arms fire.

Its most lethal weapon is a .30-millimeter Gatling gun that fires almost 4,000 rounds per minute. But top Pentagon officials now say the Warthog’s days are over. They want to eliminate the entire fleet and save $3.5 billion over five years.

Defense Secretary Chuck Hagel told reporters yesterday that money could be better spent on newer, more capable and survivable aircraft.

CHUCK HAGEL, Secretary of Defense:The A-10 is a 40-year-old single-purpose airplane originally designed to kill enemy tanks on a Cold War battlefield. It cannot survive or operate effectively where there are more advanced aircraft or air defenses.

KWAME HOLMAN:Retired General Norton Schwartz agrees with the defense secretary. He closed down some Warthog units when he was Air Force chief of staff from 2008 to 2012. He acknowledges the A-10 is beloved, but says the Air Force has other planes that can protect troops on the ground just as well.

And Schwartz says the U.S. military’s newest warplane, the multi-mission and long-delayed F-35 Joint Strike Fighter, also can handle close air support. The F-35 is designed to replace most of the U.S. strike aircraft fleet.

GEN. NORTON SCHWARTZ, Former Air Force Chief of Staff:What you want to do is to have platforms that can perform the mission, that mission and as many other as might be required in the future.

KWAME HOLMAN:But service personnel up and down the ranks told the NewsHour the A-10 is unique.

MAJ. DANIEL O’HARA, Marine Corps: I have sort of found a soul mate, so to speak, in the A-10.

KWAME HOLMAN: Marine Corps Major Daniel O’Hara, who led a platoon in Afghanistan, says the Warthog scared the Taliban.

MAJ. DANIEL O’HARA:The psychological effect it has on the enemy, I think, is pretty clear, and I also think it has an equally positive psychological effect on friendly forces.

You see that aircraft come on station, you know what it’s capable of, you know that the enemy on the other side probably doesn’t want to mess with you while that’s — that’s in the air.

PIERRE SPREY, Member, A-10 Design Team: We are outraged at the Air Forces latest attempt to kill the A-10.

KWAME HOLMAN: Pierre Sprey helped design the Warthog in the late 1960s and ’70s. He says it was built to do more than destroy Soviet tanks and that its uniquely tough airframe made it more survivable and capable than alternative aircraft.

He says those newer planes cost much more to fly. He and other A-10 supporters mobilized to save the plane at a recent conference in Washington, D.C.

PIERRE SPREY:You are going to buy extremely expensive aircraft that cause you a much worse financial problem, right, and you are canning the cheapest airplane you operate, right, and saving a trivial amount of money.

KWAME HOLMAN: General Schwartz says improvements in cockpit cameras, radars, electronics and precision munitions mean the planes that would replace the A-10 are much better at protecting ground forces even from far above.

GEN. NORTON SCHWARTZ:Increasingly, the technology has allowed us to enjoy the same protections for friendlies through other means.

KWAME HOLMAN:But A-10 advocates say technology has limits.

LT. COL. BILL SMITH (RET.), Former A-10 squadron commander:Technology is good, but the problem with using that technology, especially the optical stuff, is that it’s like looking through a soda straw. So imagine you hold a straw up to your eye, and that’s how you have to view the whole battlefield.

KWAME HOLMAN:Retired Lieutenant Colonel Bill Smith flew Warthogs over an 18-year career, including combat missions in Afghanistan. He also participated in the save the A-10 event.

LT. COL. BILL SMITH:With looking with your eyeballs, I can turn my head around and I can see much more of the battlefield than I can with slewing that pod around. And I can see the bigger picture. I’m able to maybe catch some movement out of the corner of my eye and look down and go, oh, you know what? There’s a little bit of dust over there.

KWAME HOLMAN:A-10 advocates are getting support on Capitol Hill. Senator Kelly Ayotte, a New Hampshire Republican, wants to hold off on dumping the A-10 until the new Joint Strike Fighter proves it can do close air support. Ayotte, whose husband is a former A-10 pilot, says the Air Force should find other places to save money.

SEN. KELLY AYOTTE, R-N.H.:The Air Force spent a billion dollars on an I.T. system that they’re not going to get anything out of and they just canceled in 2012. So I think we should take a step back for a minute and make sure that there aren’t any more of those billion-dollar systems out there.

KWAME HOLMAN:But General Schwartz says the days of such wasteful spending by the Pentagon are over and that today’s shrinking military budgets mean programs like the A-10 are a luxury.

GEN. NORTON SCHWARTZ: The dilemma is, what else in the Air Force do we stop doing in order to keep the A-10? So what child care center do we not keep open? What base do we compromise security?

KWAME HOLMAN:Pierre Sprey says the Air Force has mounted a campaign to retire the A-10 by making political and spending deals across the country.

PIERRE SPREY:They have reached out to state governors, state adjutant generals of the National Guard, to basically to bribe them to not complaining about losing their A-10s, promising them something, an F-16 squadron, a KC-46 tanker squadron, whatever the payoff is state by state.

KWAME HOLMAN: Staff to several members of Congress, who would speak only on background, told the NewsHour the Air Force had promised to station new aircraft in their member’s state to replace the A-10. They said, as a result, their lawmakers weren’t complaining about the A-10′s retirement.

General Schwartz said he doubts the Air Force is bartering like that, but if they are:

GEN. NORTON SCHWARTZ: The effort that Secretary Donley and I made ran into some headwind. And if the decision of the current serving leadership is that they — they want to choose to reduce some of that headwind after that painful experience, I offer no objection.

KWAME HOLMAN:Whether Congress goes along with the Air Force’s plans to retire the Warthog remains to be determined. Pierre Sprey says ground forces need the protection the A-10 provides.

PIERRE SPREY:What is at stake is the lives of a lot of troops. Troops, in the field, we owe them the ability to pull them out of trouble.

KWAME HOLMAN: General Schwartz says, that won’t change, even without the A-10.

GEN. NORTON SCHWARTZ: Our airmen, when they hear this call, troops in contact need help now, you should have no doubt that Air Force airmen are going to speed to that point and take care of business.

KWAME HOLMAN:Back at Martin State Airport, pilots and ground crews continue train on and maintain the A-10. The question is, for how long?

GWEN IFILL:We will have more with Warthog designer Pierre Sprey, who knows the plane inside and out. That’s on our home page.