At the very beginning of the film, Ming and his henchman are discussing "an obscure body in the SK system", which the inhabitants refer to as the planet "Earth", pronounced as if the word is completely foreign to them. However, at that moment, Ming activates a button on his console labeled "Earth Quake".
In the same fight, Flash's shirt (that he wore in Aboria) goes from clean to dirty and then clean again.
Again in the same fight, some of the spikes on the fighting platform can be seen folding under both Prince Barin and Flash's body as they fall on them (watch closely as the scene changes quickly), clearly showing that the spikes are made of rubber.
During the fight between Flash and Prince Barin, the cuts on both men from the whips (especially the cuts on the face) change positions and sometimes disappear altogether.
When one Ming's guards looks through a porthole of Zarkov's crash-landed ship, it seems that he is just outside. The next shot reveals a crowd of guards, but they are behind the ship and far away from the capsule.
At stake during the film is the collision of the moon with the planet Earth. Flash manages to stop Ming right before the countdown to impact runs out. However, if the moon's orbit were disrupted and it was brought closer to the Earth (especially a few seconds/minutes from collision), it would at best be caught in a deteriorating orbit and crash into the Earth anyways.
When Princess Aura is showing Flash how to fly the ship when they are traveling to Arboria, she tells him, "The left lever controls direction, and the right controls altitude". Moments later while still flying, Aura tells Flash to take a left over Frigia. She pushes on the right control lever.
In the shot of the Ajax cruiser after the Hawkmen have taken it, it is seen with a swarm of Hawkmen following it. During this shot, the superimposed Hawkmen are not composited in for the first frame.
As the Ajax approaches the city, the smoke emerging from it is retained within a rectangular border which moves in steps as the Ajax drops downwards.
There are many blue-screen compositions where characters or items appear partly transparent. This is probably due to the copying process for the travelling mattes that were used to superimpose the effects shots over one another.
When Flash holds out his hand to help Baron over the edge of the tilting combat platform, one of the spikes bends as Flash's leg pushes against it.
After General Kala announces the execution of Zarkov and Barin, there is a small scene when the gold faced guards are lined up and ordered to march by their superior (in some distorted voice). The distorted voice matches the mouth movements of the superior for several words, then doesn't as his mouth is closed. However, the voice continues to sound off.
When Flash is hiding from the Ajax in the cloud, in one shot you can see the stage on which the scene was filmed for two frames.
The wires holding the flying tracker are clearly visible as it flies upwards after destroying Zarkov's gun.
Princess Aura is apparently Ming's daughter but when she is whipped it's clear that she is red-blooded but when Ming is speared at the end of the film he has green blood.
Flash somehow manages to set a countdown of 3 minutes 21 seconds to Earth's destruction, according to Zarkov's calculations. He does so without a reference point of time.
On Ming's console listing catastrophes, Typhoon and Hurricane are listed as separate items. Typhoons and Hurricanes are the same weather system and are just called by different names around the globe.