WASHINGTON— The Air Force kicked off a demonstration of light attack aircraft on Monday as two companies — L3 and Air Tractor — made a last-minute announcement that they would participate in the experiment.

The announcement injects a fourth aircraft into the Air Force’s OA-X demo at Holloman Air Force Base, New Mexico. L3 and Air Tractor will put forward the AT-802L Longsword, the companies stated in a press release.

The A-29, built by Sierra Nevada Corp. and Embraer, and two Textron aircraft — the Scorpion jet and Beechcraft AT-6 Wolverine — will also fly.

“We are proud of the Longsword and the opportunity to participate in OA-X. We are looking forward to flying at Holloman AFB and showcasing our capabilities to the Air Force and to our partner nations,” Jim Hirsch, president of Air Tractor, said in a news release.

The AT-802 is a crop duster made by Air Tractor, which in its “Longsword” configuration is modified by L3 to carry weapons and an electro-optical infrared (EO/IR) sensor, turning it into a light attack aircraft. The AT-802L is equipped with L3’s Wescam MX-15 EO/IR sensor and ForceX mission management system, and the company also installs a glass cockpit as part of the modification process.

In terms of weapons-carrying capability, the Longsword has 11 hard points and can carry 6,200 pounds of fuel or munitions, including precision-guided weapons with the addition of a laser designator, according to information on L3’s website.

The aircraft offers more than 10 hours of endurance without needing to be refueled, and can traverse 400-mile ranges while still staying on station for about six hours. It can also take off from unimproved fields, eliminating the need for a paved runway, L3 stated.

“The AT-802L Longsword provides a highly effective capability based on a rugged, proven platform that adds class-leading technologies integrated by L3 for a simple, yet powerful solution,” said Jim Gibson, L3’s president of platform Integration and its aircraft systems sector.

Over the past month, rumors had swirled around L3 and Air Tractor’s participation in the OA-X demo. However, the companies opted to keep their role under wraps as their potential competitors hyped their own offerings.

The A-29 and AT-6 were slated to fly in the first round of the demonstration, which began today. The Longsword will likely begin operating during the second portion, along with the Scorpion jet.

Air Force officials, including Chief of Staff Gen. David Goldfein and Secretary Heather Wilson, have made clear that the OA-X experiment is not a competitive fly off, meaning that the Air Force has no obligation to purchase any of the participating aircraft. Instead, the service intends to test whether any of the offerings can meet its needs in the Middle East and help shape a requirement ahead of a possible — but not yet definite— program of record.

The AT-6 Wolverine and A-29 have already arrived at Holloman, and Air Force pilots and weapons system operators have been trained by company test pilots to operate the aircraft. Executives from both Sierra Nevada and Textron told Defense News they expected the OA-X experiment to start on July 31 and last from four to six weeks. The Scorpion jet was slated to arrive on July 28, Bill Harris, Textron’s vice president of Scorpion jet sales, said earlier this month.

During the experiment, Air Force operators will put the planes through their paces in a number of scenarios, testing the performance of the aircraft as it gathers ISR, drops weapons and operates in austere environments.

Although the Air Force has not said how large a potential program of record might be, Sen. John McCain, the Arizona Republican who chairs the Senate Armed Services Committee, recommended the procurement of 300 light attack aircraft in a white paper released earlier this year.