Older fighter jets such as the F-16 and F/A-18 will never match the F-35, an Air Force general said.

Brig. Gen. Scott Pleus, a former F-16 Fighting Falcon pilot who directs the F-35 Joint Strike Fighter program’s integration office, said even upgraded versions of the fourth-generation fighters simply can’t compete against the newer aircraft’s stealth superiority.

“You cannot take an airplane like an F-16 and really make it stealthy,” Pleus said in an interview with Military.com on Wednesday at the Pentagon. “The airplane is the shape of the airplane, the size is the size of the airplane,” he said.

“The radar cross-section of an F-18 is the radar cross-section of an F-18 — you can’t change that,” he added. “Low observable technology, the ability to evade radar if you will, is something that has to be designed into the airplane from the very beginning.”

Pleus’ comments came just weeks after President-elect Donald Trump took to Twitter to criticize the F-35 program — the Pentagon’s biggest acquisition program estimated at nearly $400 billion for almost 2,500 aircraft.

“Based on the tremendous cost and cost overruns of the Lockheed Martin F-35, I have asked Boeing to price-out a comparable F-18 Super Hornet!” he tweeted.

As previously noted on this blog, the Boeing-made F/A-18E/F Super Hornet doesn’t offer the same level of stealth or sensor technology as the F-35 Lightning II, though the Chicago-based aerospace giant has argued that the capabilities of the twin-engine electronic attack variant EA-18G Growlereclipse the Joint Strike Fighter’s stealth advantage. And, of course, the Super Hornet is significantly cheaper.

For military pilots, the statements by Pleus, the brigadier general, won’t come as a revelation. But Trump’s comments have spurred a debate on whether defense contractors can upgrade fourth-gen fighters to somehow operate like a fifth-gen fighter.

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Pleus, who has 153 flight hours in the F-35 and more than 2,000 in the F-16 — explained the closest they could get to making a fourth-gen fighter into a “4.5-gen” fighter is by adding some newer technologies, limited by the original mechanics of the aircraft, cooling and generator systems, among other issues.

“What you can do is take a fourth-generation aircraft and put a very good radar in it — so it’s a piece of technology that the F-35 has, and so you’ve upgraded it.”

Enhancing it, “more in the sensor itself,” can get a fighter like the F-16 — flying since the early 1980s — or F/A-18 a step closer to fifth-gen, “but you cannot add on stealth technology to an airplane.”

Pleus detailed the advantages the F-35 brings to the table: rapid computer technology, radar-evading stealth and what he called survivability.

“The idea is, the F-35 was developed to go into a highly contested area, both air-to-air threats and surface-to-air threats, drop its bombs, hit the targets it’s supposed to, and then come home — and that is the entire fifth-generation package,” he said.

Flying a fourth-gen or fifth-gen, from a pilot’s perspective, is “not a big change,” he said. The cockpit of the F-35, however, has bumped up situational awareness capabilities of how pilots can see or detect friend or foe in the airspace or down below.

In an F-16 for example, “If my radar doesn’t see it, then I don’t see it,” Pleus said.

“In the F-35, if my radar sees it, or if my electronic warning system sees it … or my wingman’s radar sees it, or their wingman’s radar sees it, I see all of it.”