Kim Ju Ae, the teenage daughter of North Korean leader Kim Jong Un, has driven a tank during army training supervised by her father, the pair’s latest joint public appearance fueling outside speculation that the girl is groomed as Kim’s heir. Kim oversaw an offensive tactical drill involving tank units and infantry troops on Thursday and called for completing war preparations.

Images showed Kim’s daughter sticking her head out of the driver’s hatch of a moving, olive green tank while her smiling father sat on top with three soldiers. Observers say the girl’s position showed she was driving the armored vehicle.