I know there's a question here which addresses the "it is invisible" claim. What I want to ask here is based on the two of the earliest (and most detailed) claims that Trump made on the topic, according to a Task & Purpose article:
Oct. 3, 2017: “Amazing job, and amazing job. So amazing that we’re ordering hundreds of millions of dollars of new airplanes for the Air Force, especially the F-35. Do you like the F-35? I said how does it do it in fights, and how do they do in fights with the F-35. He says we do very well, you can’t see it. Literally you can’t see. It’s hard to fight a plane you can’t see right? But that’s an expensive plane you can’t see. And as you probably heard we cut the price very substantially, something other administrations would never have done, that I can tell you.”
Nov. 23, 2017: “The Navy, I can tell you, we’re ordering ships. 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. 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.”
Some of that sounds quite improbable a pilot would have told him, basically the "right next to it" part and probably even "literally you can't see it". But is the bulk of Trump's claim that he was told by "Air Force guys" that the enemy "can't see it" possibly based in something Air Force personnel have said? Trump didn't identify his Air Force sources but one way to check the for the plausibility that "Air Force guys" told him that is to look for similar statements Air Force personnel involved with the F-35 may have made prior to Trump's endorsement of the "can't see it" discourse.