How would the military’s new F-35 Joint Strike Fighter aircraft fare in a dogfight against an old F-16D fighter? Not well, according to a leaked test pilot report of mock air battles in January between the two aircraft.

The test pilot’s report was first reported by the website War is Boring, which covers military matters. The leaking of the report is under investigation by the Department of Defense, which says the test plane was missing some of the F-35’s most impressive technology, such as long-range abilities that allow it to avoid dogfights to begin with. FoxNews.com has seen the report, which is scathing about the F-35’s abilities at points.

“It [the F-35] wasn't effective for killing or surviving attacks primarily due to lack of energy maneuverability,” the unnamed pilot’s report concluded about the plane, which is the most expensive weapon in history and has cost more than $1 trillion dollars to develop and produce, after cost overruns.

"This report confirms what observers have long suspected -- that, despite ample warning, America made a bad bet with the F-35."

- David Axe, editor-in-chief of War is Boring

But in a statement emailed to FoxNews.com, the Department of Defense’s F-35 Joint Program Office defended their new plane, emphasizing that this particular test was done with a test F-35 called an “AF-2”, which lacks advanced equipment normally in F-35s that is designed to destroy enemy planes before they can reach the F-35.

“The F-35's technology is designed to engage, shoot, and kill its enemy from long distances, not necessarily in visual ‘dogfighting’ situations,” the statement reads, adding that F-35s have won longer-range mock battles.

“There have been numerous occasions where a four-ship of F-35s has engaged a four-ship of F-16s in simulated combat scenarios and the F-35s won each of those encounters because of its sensors, weapons, and stealth technology,” it reads.

Not everyone is convinced. David Axe, founder and editor-in-chief of War is Boring, said that the lack of simple close-combat fighting ability is a big problem.

"This report confirms what observers have long suspected -- that, despite ample warning, America made a bad bet with the F-35," Axe told FoxNews.com.

"Anyone claiming that dogfighting is obsolete needs to read some history. The Pentagon made the same claim before the Vietnam War -- and many Americans pilots died as a result when more agile MiG-21s shot down their cumbersome jets," Axe said.

Fox News reporter Lea Gabrielle, a former Navy fighter pilot, said that the Department of Defense’s statement jives with what test pilots have told her.

“F-35 test pilots have told me ‘in the F-35, if you ever get into a dogfight, something has gone way, way wrong,’ Gabrielle said. 

“I am ‘old school’ in that I believe dogfighting skills are important for fighter pilots to have, but… this aircraft should be able to eliminate the enemy well before he or she ever sees you,” she said. She added that, unlike the test plane, deployment-ready F-35s will have capabilities to prevent enemies from getting close.

“If you’re trying to measure the F-35 that will be deployed against an F-16, this wasn’t a fair fight,” she said.

The DoD statement goes on to say that the January dogfighting test found that the F-35 mostly operated acceptably.

“The dogfighting scenario was successful in showing the ability of the F-35 to maneuver to the edge of its limits without exceeding them, and handle in a positive and predictable manner,” their statement reads.

The Department of Defense also said that the unauthorized release of the test report is under investigation.

“The release of this FOUO [For Official Use Only] report is being investigated,” the statement reads.

“The disclosure of this report should not discourage our warfighters and test community from providing the Program Office and Lockheed Martin with honest assessments of the F-35's capabilities,” the statement added.

The leaked test pilot report also warned about “insufficient pitch rate” and “lack of energy maneuverability” as issues, noting that regarding energy maneuverability the aircraft was “substantially inferior” to the 1980s-vintage F-15E aircraft.

It also mentions other specific problems, noting that the size of the cockpit and the helmet seriously impaired pilot vision.

“The helmet was too large for the space inside the canopy to adequately see behind the aircraft,” the test pilot wrote, noting that there were multiple times when he would have been able to see his F-16 opponent if not for the helmet blocking his motion and vision.

The Department of Defense statement responded that the helmet would be of much more use in a fully-equipped F-35.

“[The test plane] is not equipped with the weapons or software that allow the F-35 pilot to turn, aim a weapon with the helmet, and fire at an enemy without having to point the airplane at its target,” it reads.

Lockheed Martin also defended its plane in a statement to FoxNews.com.

“As many military leaders from across the globe have stated on numerous occasions and we fully endorse - when a 4th generation fighter [such as an F-16] encounters the F-35 in a combat scenario, the 4th generation fighter dies,” the statement reads.

But David Axe says he remains skeptical despite the official statements.

“The government seems to think the F-35 will never get into a close fight. History says otherwise,” he said.

Maxim Lott can be reached at www.maximlott.com or at maxim.lott@foxnews.com