After years of discussion, the U.S. Air Force has taken the initial steps to buy commercial, off-the-shelf aircraft for its light attack aircraft fleet.

The service is alerting defense firms hoping to compete for the Light Attack Aircraft program that it intends to begin soliciting bids in December, according to a presolicitation announcement posted on FedBizOpps on Friday.

"LAA will provide an affordable, non-developmental aircraft intended to operate globally in the types of Irregular Warfare environments that have characterized combat operations over the past 25 years," the post said. "A contract will be awarded in fourth quarter of [fiscal 2019]."

While the program would remain a full and open competition, Air Force officials said the most viable aircraft are the Textron Aviation AT-6 Wolverine and Sierra Nevada/Embraer A-29 Super Tucano.

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"Sierra Nevada Corporation (SNC) and Textron Aviation are the only firms that appear to possess the capability necessary to meet the requirement within the Air Force's time frame without causing an unacceptable delay in meeting the needs of the warfighter," the FedBizOpps post said.

The two single-engine turboprop aircraft were most recently part of the service's light attack experiment at Holloman Air Force Base, New Mexico. The second phase of the experiment was canceled in July following a fatal crash.

Navy Lt. Christopher Carey Short, of Canandaigua, New York, was piloting an A-29 when it crashed over the Red Rio Bombing Range within White Sands Missile Range, New Mexico, on June 22. The Air Force temporarily suspended exercises with the two aircraft before announcing the remainder of the live-fly exercises and combat maneuvers were canceled.

A Light Attack Distinguished Visitors Day, originally set for July and canceled after the fatal crash, has been rescheduled for Sept. 14 at Andrews Air Force Base, Air Force officials said.

Lt. Gen. Arnold Bunch, top acquisition official for the Air Force, told reporters at the time that the service would continue to work with defense industry partners to complete remaining test requirements, which mostly consist of maintenance and sustainment data.

He said then that a potential request for proposal for light attack, also known as OA-X, could be issued by December.

"If we decide that we're going to go forward with the acquisition ... if that's the direction we're going to go, we want to get an RFP out on the street by December," he said last month. "If we go down that path ... what we then want to do is make a downselect decision within the next fiscal year."

The Air Force in 2016 announced plans to hold flight demonstrations with a handful of aircraft to test whether lighter, inexpensive and off-the-shelf aircraft might be suitable in ongoing wars such as Afghanistan.

As part of Phase I, four aircraft -- the A-T6 and A-29, as well as AirTractor and L3's AT-802L Longsword and Textron and AirLand LLC's Scorpion -- conducted demonstrations and weapons drops during the experiment at Holloman in August 2017. After Phase I was completed, the Air Force selected the Wolverine and Super Tucano to undergo more demonstration fly-off scenarios between May and July of this year.

In November, key lawmakers agreed to provide the Air Force with $400 million to continue experimenting with the planes. Additionally, lawmakers recently passed the fiscal 2019 National Defense Authorization Act, which authorizes $300 million "to procure Air Force light attack aircraft and associated long lead material," according to the bill's summary.

If the planes can be interoperable with other militaries' planes, the result would be a diverse fleet of aircraft with partners across the world, officials have said.

"We must develop the capacity to combat violent extremism at lower cost," Secretary of the Air Force Heather Wilson said in a statement released Monday. "Today’s Air Force is smaller than the nation needs and the Light Attack Aircraft offers an option to increase the Air Force capacity beyond what we now have in our inventory or budget."

Air Force Chief of Staff Gen. David Goldfein told Military.com in September that the light attack initiative should be viewed as a new way of doing business -- not just a plane, but part of a larger communications system.

OA-X "is actually not about the hardware -- it's about the network," he said, adding he wants the service to train more often with coalition partners who may not have high-end fighter aircraft.

"At the same that we're looking at a relatively inexpensive aircraft and sensor package, can I connect that into a network of shareable information that allows us to better accomplish the strategy as it's been laid out?" Goldfein asked.

Bunch last month added, "We're still going to experiment and try out the network in other areas over time. The goal of this network is to get it to the point where we can utilize it in other platforms beyond light attack."

-- Oriana Pawlyk can be reached at oriana.pawlyk@military.com. Follow her on Twitter at @Oriana0214.