When Fighting 8 takes off from the Enterprise (the carrier has a squared-off deck and the letters "EN") to search for the downed seaplane, one of the planes takes off from a carrier with a curved flight deck and a large "O" painted on the forward end. This would be footage of a takeoff from either the Saratoga or Lexington. Probably the Saratoga, since there are photos showing the "O" on her flight deck found online.
When the Squadron gets the call to search for the missing seaplane, the Commander says there is just one hour until darkness. Yet the following shots clearly show them taking off with the sun high in the sky.
When landing on the carrier, there is one shot of a plane landing with the carrier island on the left. American carriers always had the island on the right of a landing aircraft.
When Rhodes is acknowledges Drake via his radio while Drake is on the beach, his first response is "Plane 4 aye aye!" That is an incorrect use of the phrase aye aye which means that someone (usually a subordinate) heard an order and it will be carried out. It would never be used as radio greeting. And in this film, it's misused more than once.
When the squadron is searching for the downed seaplane, Commander Gary (Walter Pidgeon) reports to the tower that his formation of Grumman F3F-2s are flying at 10,000 feet at a speed of 300 (the units were not mentioned, but the moviegoer would logically assume 300 mph). The top speed of a Grumman F3F-2 was 264 mph. The F3F-2 could probably approach 300 mph in a vertical dive, but not in level flight as Commander Gary's planes were.
When Cmdr. Gary is in his hospital bed, after his head/brain surgery, he is still wearing his navy ring. In truth all jewelry is removed for surgery in case of swelling, for one reason.
The position of the collar rank insignia of several of the officers is wrong. The specification is that the insignia should be centered on the width of the collar and 1 inch from the leading edge of the collar. There are some officers with their insignia almost on the collar point.
Wires are clearly visible on most of the miniature aircraft.
The navigator of the PB-Y searching for the downed plane is an Admiral, which is so far away from likely as to be ridiculous. The Admiral's staff may have been coordinating the search, but he would not be out in an aircraft.