Factual error: When in flight the jet-pack is always thrusting horizontally. There is no vertical component of thrust, and so there ought to be no lift supporting it & its wearer above the ground.

Continuity: When Cliff and Peevy anchored the statue into the ground in the field to watch the rocket in action, they use a wired switch to activate the rocket. However, there's something wrong with this: there is no wire visible leading to the rocket/statue.

Deliberate "mistake": When Cliff crashes into the pond after his first flight, Peevy tells him that he has to look around with his eyes and steer by moving his head. However, just before this as he is flying next to the passenger airplane, he looks over at it, turning his head to the left without changing directions at all.

Factual error: The only ways to steer a rocket are to gimbal the nozzle or put steerable vanes in the exhaust. You cannot, ever, put a rudder on the front of a speeding aircraft.

Continuity: When Cliff is being chased by the mobsters in the fancy restaurant, he escapes by flying through a stained glass dome directly above the dance floor. Two mobsters below aim up at him and start firing as he crashes through the dome, but no glass showers down on them.

Continuity: When he first flies the GeeBee, the joystick changes colors in the different scenes.

Continuity: When Cliff and Peevey first test the rocket pack by strapping it to a statue, the statue skids across the ground and crashes into a small mound of dirt on the otherwise completely flat field. But when they run over to collect the pack, the mound is gone and the statue is lying in a crater, as if it had hit the ground from a much steeper angle.

Continuity: When Cliff straps the rocket on his back to save the pilot, he leave some of his coat's buttons undone, but when he lands in the pond, he's completely buttoned.

Factual error: There are numerous references throughout the film to "Deutschemarks" as the currency of Nazi Germany. However, these were not introduced until after the war; I think the currency they actually used were called "Reichmarks".

Factual error: With the rockets positioned on the rocketeer's back, their thrust would create an unopposed moment about his center of gravity. This would result in the flyer being slammed face first into the ground, not flying straight up. (Note that functional rocket packs, such as were flown briefly in "Thunderball", place rocket nozzles on either side of the flyer's torso, not both on his back.)

Continuity: When Cliff first puts the Rocket on to save Malcolm, he doesn't do his helmet strap up. When they walk outside, just before Cliff takes off he turns back round to Peabody and his strap is done up.