When on the test flight, the pellet of poison gas is supposed to roll forward off of the shelf when the plane goes into a dive. Charlie Chan and Richard Jeffery are at the front of the plane and in front of the shelf. Herbert Fenton is at the rear of the plane and at the rear of the shelf. The plane dives but instead of the pellet rolling forward towards Charlie Chan, it rolls backward and Fenton catches it. That would have been impossible.
When Jimmy runs out to the tarmac at the airport, to see his pop, Charlie Chan, he ends up standing facing him, with Hugh Drake between them. Then there's a studio shot where Jimmy is standing next to Charlie, not across from him, with Hugh Drake opposite.
Seemingly an hour or so after Drake's body is discovered in his apartment, Charlie gets a toxicology report over the telephone from the city morgue naming the specific poison that was in his body.
As shown by its row of square upper windows, the aircraft seen in the opening scene (as well as its "arrival in New York") is a "DST" - Douglas Sleeper Transport - a variant model of the more-common DC-3. The model shown briefly "inflight" is a completely different airplane entirely.
Charlie asks Jimmy to identify a chemical smell. Jimmy, only an undergraduate student, immediately recognizes the smell of a poison gas invented only months before and gives his father background information on it.
When looking at the photos in Drake's briefcase, the wrong actress is shown as the killer's wife.