When the plane is first coming in for a landing, still bouncing on the rough ground, the propeller comes to a stop. Moments later, as the plane actually stops, the propeller is still turning at full speed, and then stops again.
In the ground shots the plane has registration number N6647M and a V antenna. In the airborne shots it's N8228K, with a loop antenna.
After the governor's guard is punched out and the foursome are making a quick getaway, only the pilot is visible in the passenger cabin of the rather small plane. The other three, who look tightly packed moments before, are not visible at all.
Early at the bar, Lon Chaney's beer keeps gong from 3/4 and foamy to 1/4 empty.
For a couple of scenes in the middle of the movie, Gloria Talbott's shirt changes from light to dark, then back to light again, but with the same torn right sleeve.
After landing, and Lon Chaney and the pilot are thinking about leaving the rest of the group by stealing the plane, Look closely, the planes wheels are still chocked with rocks. They could not have taken off.
When he's battling the giant snake, the activity causes the back of the Cyclops' rubber bald cap to separate from his neck. The latex flap can be seen dangling for the rest of the scene.