A group of U.S. Army soldiers was posing for a photo next to an F-35 fighter jet's engine when the engine suddenly started running. What looked like a routine souvenir picture instantly became a startling moment, and it is the kind of scene that gets people talking. The F-35 is powered by a single Pratt & Whitney F135 turbofan, a powerful engine built for one of the world's most advanced fighter jets. Basic details, including where and when it happened and whether anyone was hurt, have not been confirmed.

Running jet engines can be dangerous to anyone standing close by, which is why ground crews normally keep strict safety distances during startup and operation. That makes the clip especially interesting to viewers, since the soldiers were posing right beside the engine as it came to life. Questions remain about why the engine started, whether it was a planned test or ground check, who was operating it, and whether the soldiers knew it might happen. No official explanation has been released, so it is best to wait for details from the military before drawing any conclusions.