Few aircraft in the U.S. Air Force's arsenal attract as much support as the A-10 Thunderbolt II Warthog.

In a fit of martial poetry, Mother Jones describes the A-10 as "an unstoppable commercial Learjet with a full-automatic cannon in its nose and an iron bathtub surrounding the cockpit." More laconic, Foxtrotalpha simply states that the A-10 is "the best CAS [close air support] platform mankind has ever designed."

Good as the A-10 is, however, even its supporters acknowledge that it must one day be retired. In anticipation of that day, the Air Force has been spooling up a "capability assessment" preparatory to acquiring a new ground attack aircraft that could, possibly, fit the bill. It's call the OA-X competition, and one year after it was announced, OA-X could finally be entering its final innings.

A Scorpion fighter jet in flight.

Textron's Scorpion jet comes loaded for bear. Image source: Textron.

What is OA-X?

OA-X aims to identify a "light attack" fighter -- preferably one already designed and able to be bought "off the rack" -- that could fill in for the aging A-10 in close air support roles.

No plane could completely replace the A-10, of course. That's because no other airplane has ever been designed to carry the 600-pound, 20-foot-long GAU-8/A Gatling gun that is the A-10's most famous feature. But an OA-X aircraft equipped with air-to-air missiles and smart bombs, ground attack rockets, and .50-caliber machine guns could probably do in a pinch -- especially if the Air Force buys 300 of them, which seems to be its intention. 

Who will win OA-X?

The big question now is which plane will ultimately get picked to serve as the Air Force's OA-X. The Air Force has settled upon three contenders. 

This summer, Embraer's (NYSE:ERJ) A-29 Super Tucano fighter plane, built in cooperation with Sierra Nevada Corp., will participate in a fly-off against two aircraft built by rival Textron (NYSE:TXT). One, the AT-6 Wolverine, is an upgraded version of Textron's T-6 Texan aircraft that competed against the A-29 for a contract to outfit the fledgling Afghan Air Force back in 2012. (That was back before Textron bought the AT-6's maker, Beechcraft). Similar in appearance, both airplanes are propeller-driven aircraft, and it took nearly a year of legal skirmishing before that contract was ultimately awarded to Embraer.

Today's contest could be even more hotly contested.

That's because, whereas the contract to build airplanes for the Afghans concerned a sale of only 20 airplanes, with OA-X, there's a 300-plane order at stake. Given that the 2012 contract was valued at $427 million, the much larger OA-X deal could yield closer to $6.4 billion for its winner. Expect a heated dogfight over that money the next time AT-6 meets A-29 in the skies.

Textron's secret weapon

Given that the last time these two aircraft went head to head, the Embraer came out on top, you might expect this second engagement to yield the same result -- but don't be too sure about that. This time around, Textron is bringing two guns to this fight. In addition to bidding the AT-6 for the Air Force's OA-X needs, Textron will also be offering to sell the Air Force its self-developed Scorpion fighter jet -- and here's where Textron could have a clear edge.

Jet-powered, Scorpion can reach a top speed of 517 miles per hour  -- 150 mph faster than Embraer's prop-driven A-29. Scorpion also boasts a flight ceiling of 45,000 feet, two miles higher than the Super Tucano, and can carry 3,000 pounds worth of ordnance in an internal weapons bay, and another 6,200 pounds mounted on six hardpoints attached to its wings.

Combined, that's about three times the destructive power that Super Tucano brings to the fight. Yet Textron is reported to be offering Scorpion for sale for less than $20 million per plane -- cheaper than the $21 million price  the Pentagon paid for Afghanistan's A-29s.

At the same time, Popular Mechanics reports that the Air Force is looking for an airplane that costs "about $4,000 to $5,000 an hour" to fly. Although higher price tags aren't usually a plus in Pentagon contract bids, that target price appears aimed at ensuring Textron's Scorpion jet (advertised cost per flight hour: $3,000) can compete against Embraer's Super Tucano (experienced cost per flight hour: $1,000). If you assume, as I think we must, that the Pentagon was aware of what airplanes might be bid for OA-X, you have to wonder if the Air Force set up this competition with a good idea of which plane it wanted to win.

Seems to me, that's the Scorpion jet. Seems to me, that's Textron. 

Rich Smith has no position in any stocks mentioned. The Motley Fool recommends Embraer-Empresa Brasileira. The Motley Fool has a disclosure policy.