The first sign of trouble came on Thanksgiving 2017. Donald Trump was in south Florida, speaking to Coast Guard personnel near one of the president's golf resorts, and generally spoke about how pleased he was with himself.

But part of his unscripted remarks touched on a subject Trump seemed to find fascinating. "With the Air Force, we're ordering a lot of planes, in particular the F-35 fighter jet, which is, you know, almost like an invisible fighter," he said. "I was asking the Air Force guys, I said, 'How good is this plane?' They said, 'Well, sir, you can't see it.' I said, yeah, but in a fight -- you know, a fight, like I watch in the movies -- they fight, they're fighting. How good is this? They say, 'Well, it wins every time because the enemy cannot see it. Even if it's right next to it, it can't see it.' I said, 'That helps. That's a good thing.'"

As we discussed at the time, Trump had previously explained that the F-35 is undetectable by radar, but this appeared to be the first time the president had publicly made the case that an enemy couldn't see the fighter jet, even if they were "right next to it."

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Yesterday, Trump was in Warren, Michigan, ostensibly to speak about the revised version of NAFTA, though he briefly spoke about the F-35 and the possibility that the jets may be deployed to a nearby National Guard base.

"We're giving strong consideration to deploying some of our mighty F-35s to Selfridge Air National Guard Base. And you know what that means, right? You know what that means. That's a big deal. "So, Selfridge, you're going to see a lot of very fast planes. Actually, they're totally stealth, so maybe you won't see them come in. Okay? You won't see them come in, but they're coming in."

I'm reasonably sure Trump thinks F-35s are literally invisible.

To be sure, the president routinely references the fighter jet and frequently tells supporters that the enemy can't see it. But I usually shrug that off, because in context, there was a way to generously interpret his comments in a figurative way.

Once in a while, though, Trump slips and suggests he genuinely believes the plane has sci-fi cloaking technology -- as if Wonder Woman were some kind of documentary.

I can't take credit for this joke, but after I first wrote about this a couple of years ago, a reader told me he wanted to see officials escort the president into an empty airplane hangar, point in a vague direction, and tell him, "The F-35 is right there," just to see what he'd do.

And for those keeping score, this is the latest addition in the Trump-says-odd-things-about-planes franchise, which has proven to be more robust than I ever expected.

MORE: Today's Maddowblog