"Sometimes, stuff happens..." is the title of a photo in a slideshow on "challenging design projects" from Sandia National Laboratories. The image appears to show a nuclear-capable air-launched cruise missile that's been dropped off a trailer and run over by a truck, two experts told Business Insider, raising concerns about the possibility of an accident involving a nuclear weapon.

Let's take a close look at the picture:

Sandia National Laboratories and Business Insider

The Air Force told Business Insider the photo was dated, as the uniforms worn by airmen in the picture were phased out in 2011. It said it conducted an internal investigation, but it shared no conclusions with Business Insider.

Officials at Sandia said the photo was at least 15 years old and that they are "confident that what you see there is either a training aid or a non-nuclear cruise missile." However, Sandia refused to establish how it knew the missile was non-nuclear. Sandia said it didn't know when or where the picture was taken or what happened in the photo.

"By putting that picture in the presentation about nuclear-weapon safety, the obvious implication is that this was an accident involving a nuclear weapon," Stephen Schwartz, an independent nuclear-weapons policy analyst and consultant who wrote "Atomic Audit: The Costs and Consequences of US Nuclear Weapons Since 1940," told Business Insider. Schwartz first spotted the image.

"Otherwise you could use any type of accident picture," Schwartz said. "There are other pictures of well-known nuclear accidents one could use going back into the 1950s."

Eric Schlosser, the author of "Command and Control: Nuclear Weapons, the Damascus Accident, and the Illusion of Safety," has chronicled nuclear accidents across the history of the US's nuclear arsenal. He agreed with Schwartz's assessment.

"That sure doesn't look good," he said.

Business Insider contacted a former official in the weapons department of Sandia, who said the object in question was not an air-launched cruise missile — or a missile at all — but rather an external fuel tank.

Yet this explanation did not hold up to experts' scrutiny.

Here are some examples of external fuel tanks, which jets carry to extend their range:

Compare them with the trapezoidal shape of the AGM-86, the US's nuclear-capable air-launched cruise missile:

Note the ridge toward the nose of the object, near where the truck seems to have run it over. That ridge is consistent with the AGM-86. Additionally, the object appears to have an air intake toward the tail, which no external fuel tank for a jet would have.

These fuel tanks are round with pointy ends. Other shapes of fuel tanks exist for other planes, but none feature air intakes. US Air Force and Sandia National Laboratories

Schwartz concluded that the object was some older version of the AGM-86, which has undergone slight redesigns over time.

So was it a nuclear or nuclear-capable missile?

No one seems to know for sure. The US manufactured conventionally armed AGM-86 missiles, and it has certainly made training aides that look like the AGM-86.

But Schwartz said that out of countless photos of known incidents Sandia could have picked to represent an accident with a munition, he found it curious that Sandia selected this image.

Could the missile have detonated?

An AGM-86 ALCM is loaded onto a B-52 at Minot Air Force Base. These updated AGMs have a slightly different shape than the earlier ones, pictured above. Senior Airman Kristoffer Kaubisch or Senior Airman Andrew Crawford

Schwartz said that as alarming as the picture was, the US's nukes are so stable and responsibly made that even if you dropped one off a trailer and ran it over with your truck, "it will not cause it to detonate with a nuclear yield."

"The worst-case scenario — and it doesn't look like it happened — would be the conventional high explosives detonate and scatter plutonium across the area," said Schwartz, who explained that nuclear cruise missiles contain both a conventional explosive and a nuclear core. The nuclear core would certainly not have been armed in this situation, thereby eliminating a nuclear detonation as a possibility.

"Clearly just the front section with the radar and altimeter" were smashed, said Schwartz, who added that the nuclear core sits farther back in the missile.

"Conventional high explosives are somewhat unstable," he said. "But obviously there was no fire here, and pure crushing wouldn't necessarily cause an explosion.

A Sandia Labs mechanical engineer adjusts a microphone for an acoustic test on a B61-12 system. Sandia Labs/Randy Montoya "The next worst thing would be: Is the weapon a loss? Is it possible to repair the missile?"

Nuclear missiles, even training aids, can cost millions. So while the accident at worst posed a small risk of an explosion that would spread radioactive materials — not a nuclear detonation — it was likely still a costly mistake.

"Something happened, and it wasn't the weapon's fault," Schwartz said.

According to Sandia, this picture was included in the slideshow to demonstrate an immutable fact about even the most responsible pursuits: "Human error can occur despite concerted efforts to achieve 100% safe operations."