As the F-35 Joint Strike Fighter program barrels toward its final major testing process before full-rate production, program leaders say a much-discussed comparison test between the beloved A-10 Thunderbolt II and the new 5th-generation fighter is very much still in planning, and could kick off as soon as next month.

In a roundtable discussion with reporters at the F-35 Joint Program Office headquarters near Washington, D.C., on Wednesday, the director of the program said the final test and evaluation plan is still being constructed. That will determine, he said, when the A-10 vs. F-35 test begins, and whether it happens in the main test effort or in an earlier, more focused evaluation.

"The Congress has directed the [Defense Department] to do comparison testing, we call it," Vice Adm. Mat Winter said. "I wouldn't call it a flyoff; it's a comparison testing of the A-10 and the F-35. And given that the department was given that task ... that is in [the] operational test and evaluation plan."

Initial Operational Test and Evaluation, or IOT&E, is set to begin for the F-35 in September. But two new increments of preliminary testing were recently added to the calendar to evaluate specific capabilities, Winter said.

The first increment, which was completed in January and February, took place at Eielson Air Force Base in Alaska and evaluated the ability of the aircraft to perform in extreme cold weather conditions, with a focus on the effectiveness of alert launches. The results of those tests have yet to be made public.

The second increment, set to begin in April, will focus on close-air support capabilities, reconnaissances, and limited examination of weapons delivery, Winter said. The testing is expected to take place at Edwards Air Force Base in California and other ranges in the western United States.

Questions surrounding the F-35's ability to perform in a close-air support role are what prompted initial interest in a comparison between the aging A-10 "Warthog" and the cutting-edge fighter in the first place.

The requirement that the two aircraft go up against each other was included as a provision in the National Defense Authorization Act for 2017 amid congressional concerns over plans to retire the A-10 and replace it with the F-35.

In an interview with Military.com in 2017, Air Force Brig. Gen. Scott Pleus, then-director of the F-35 program's integration office, said he expected the A-10 to emerge as a better CAS platform in a no-threat environment.

But the dynamics would change, he said, as the threat level increased.

"As you now start to build the threat up, the A-10s won't even enter the airspace before they get shot down -- not even within 20 miles of the target."

-- Hope Hodge Seck can be reached at hope.seck@military.com. Follow her on Twitter at @HopeSeck.