In the 1960s, NASA commissioned Grumman Aircraft to build 15 space-worthy lunar modules, or LMs, for its Apollo program.

The fate of 14 modules is well-documented, but the last — LM-14 — is harder to account for in historical records. We attempted to track down and piece together the mystery of the seemingly missing moon lander.

Most experts we contacted weren't sure where it had gone, but we finally got a convincing answer (with documentation) from one space historian and artist.

He believes the lander was scrapped and its aerospace-grade metal possibly reused in jet fighters.

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Following is the transcript of the video.

Narrator: NASA has released photos, videos, and audio recordings of its Apollo missions.

Audio clip: We copy you down, Eagle.

Narrator: So there's little left about these missions that we don't already know, except for one mystery that's been hiding in plain sight for decades. One of NASA Apollo lunar modules may be missing. That's right, missing. And not even NASA seems to know where it is.

Audio clip: Engine's on five, four, three, two, all engine's running. We have a liftoff.

Mosher: Where is Lunar Module 14? What state was it in? Does anybody have it? Does anybody know where it's at?

Narrator: From 1962 to 1970, NASA commissioned Grumman Aircraft to build 15 space-worthy lunar modules for its Apollo program. Each one was was labeled Lunar Modules 1 through 15 and cost around $150 million to make, or about $1.1 billion today.

Audio clip: Charlie Brown was selected by the astronauts as the codename for the Apollo 10 command module and his friend Snoopy was the call sign for the lunar module.

Mosher: NASA launched 10 of these lunar landers into space. Six of them landed on the surface of the moon and brought the astronauts back. Other four were used for practices and dry runs, future missions. And there were five that were left on the ground.

Narrator: Three of those five that never went to space, Lunar Modules-2, 9, and 13, are in museums, which leaves us with LM-14 and 15.

Mosher: Lunar Module 15 was another lunar lander that was being build for Apollo 20, which of course never happened. They turned it into scrap metal. So that leaves us with one lunar lander, LM-14. On the Smithsonian's website, there's a page listing the lunar landers and all of their fates. Lunar Module 15 is listed as scrapped but if you go up one row and you look at Lunar Module 14, it says not used. What that means, we don't know, and that's what started this adventure in the first place.

Narrator: To be clear, it is not easy to hide one of these landers. Once complete, they're the size of a small house and weigh about 35,000 pounds.

Mosher: Now when we started into Lunar Module 14, things are a little weird. The documents that we have access to said incomplete or not used. It didn't say anything about it being scrapped. It didn't say it was in any institution or museum. And so we started digging into this.

Narrator: NASA and the Smithsonian didn't have evidence to its whereabouts, the Cradle of Aviation Museum didn't know, and even historians at Northrop Grumman, the original manufacturers of the lunar modules, were stumped.

Mosher: But one of the experts that we talked to said, "hey, I think it's at the Franklin Institute "in Philadelphia". We looked into that and it was not it. It was an early prototype from the Apollo program, a lunar module that was never supposed to fly into space.

Narrator: And then we got a lead, sort of.

Mosher: There was a document from March, 1978 that is a disposition, or a list, of everything in the Apollo program. What it was, what its code number was, and where it's located. And that document is missing page number nine, which is the page that describes where Lunar Module 14 would be located or what happened to it, if anything.

Narrator: Yeah, it sounds exactly like some sort of Hollywood spy thriller, but this actually happened. Nobody could find this document. Even one of NASA's historians looked for us and couldn't locate it. And the same went for the National Archives. We finally got some clue as to what happened to it from University of Houston's Space Archive.

Mosher: Hi, this is Dave Mosher with Business Insider. Is this Jean?

Jean: Hi, yes it is. Hi, Dave.

Mosher: Hi. So I heard you found page nine of that document. Can you read it to me, tell me what is says?

Jean: Next to LM-14, it says mission cancelled.

Mosher: Mission cancelled. And then is there anything else that it says?

Jean: The next column says remarks. It says deleted from program.

Mosher: Deleted from program. It doesn't say where it went or what happened to it?

Jean: No, it does not.

Mosher: Okay.

Narrator: So we were at a dead end. And to be fair, this wouldn't be the first time a moon lander has been lost to history. In 1969, the lunar lander for Apollo 10 was ejected into space as part of a dry run for Apollo 11.

Audio clip: Ground contact was maintained with the ascent stage until its batteries were depleted, some 12 hours later.

Narrator: NASA didn't track the lander at the time, so it was missing, floating somewhere in space for decades. Until, in 2019, a group of enthusiasts from the UK said they were pretty sure where it was floating in space. So if those guys could find a lost lunar module in the vast expanse of space, why does nobody know where a moon lander on Earth has gone?

Audio clip: Okay, this has got to be the greatest site ever.

Narrator: So we had pretty much given up on uncovering the truth. That was until we got ahold of Paul Fjeld a few weeks later. He's obsessed with these lunar landers.

Mosher: In fact, he worked with Cradle of Aviation Museum to retrofit LM-13 into an Apollo-style landing site within the museum.

Narrator: So here's what he had to say about our grand missing lunar lander mystery.

Fjeld: 14 actually never really got built. I'm not gonna bet my son's life, but I'll bet a lot of money that there's not a scrap of LM-14 left.

Narrator: Of course, that would explain why there's no photos of it.

Mosher: The really revealing thing that Paul showed us was this progress chart from Grumman Of the lunar landers that were under construction right before NASA canceled the entire program and it shows that LM-14 was about 1-5% complete based of Fjeld's analysis. So the farthest that technicians at Grumman got was basically cutting out all of these pieces of metal and starting to assemble them, weld them together, before NASA canceled the program. We also spoke to two other space flight history experts and they also think that LM-14 was scrapped, but they're not entirely certain of that.

Fjeld: I'm gonna say they would've said, "look, we got a bunch of F-14s "that are just starting to come off the line here. "This is what's the future for Grumman. "We need all the metal that we can get. "This is some lovely 2024 aluminum, "7075 structural aluminum. "Can we use that on F-14s?" "Sure."

Narrator: So LM-14's frankensteined pieces maybe did fly, in a way. And perhaps they're in an aviation museum right now, as part of a jet.

Audio clip: In this strange, metallic bird rides the ancient and endless dream of all mankind.

Narrator: But we may never know for sure.

Fjeld: I can't guarantee that some guy didn't just drive it off the lot and it's now sitting in his basement or up in an attic that his grandkids have no idea what the hell it is. Who knows?