Revealing mistake: In the final scene where Fonda and Holbrook are looking over the carrier at the crowds on the dock you can see that only the first rows of people are dressed in period clothes, the rest of the crowd are dressed as they would have been in 1976 when the film was made.
Continuity mistake: During the scene when Torpedo Eight squadron is slaughtered during its attack on Nagumo's carriers, Ensign George Gay's aircraft changes appearance several times. This is due to the different snippets of wartime footage being cobbled together. When the squadron commences its attack, his plane is a Vindicator. When his plane is the last one left, it has changed into an SBD Dauntless. When Gay's plane has been hit and is diving towards the sea, it has become an Avenger. Finally, when his aircraft hits the water, it has become a Hellcat.
Continuity mistake: When the American torpedo bomber attacks the first carrier, it gets shot up and flies past the carrier, crashing into the sea, at which point it becomes a single seat fighter.
Other mistake: Another "Recycled Footage Segment" via Tora! Tora! Tora!: When 3 Officers on Midway come out of their bunker and say that the runway is still operational, the footage of the B-17 with the landing gear problem mentioned elsewhere is blatantly used.
Factual error: American carriers did not have angled decks until after W.W.II.
Factual error: Several shots identifying the American and Japanese carriers are actually those of late W.W.II and Korean War era Essex-class carriers.
Revealing mistake: Utility poles are visible in the scene of the Japanese aircraft carrier launching planes for the first attack on Midway.
Revealing mistake: In virtually every shot of the flight deck looking up at the fighters and bombers overhead attacking the U.S. ships, the anti-aircraft guns show the red paper caps of the blanks rather than pointed bullets.
Revealing mistake: Still another "Recycled Footage" sighting, plus a double error in one: A scene has a truck blown up during the "attack" on Midway by a Japanese Fighter Plane. Same footage (a bit cut for time) from "Tora! Tora! Tora!" and Midway is small enough that trucks of that size weren't used on the Island.
Factual error: During the Battle of the Coral Sea, an admiral orders that the TBD's (Torpedo Bomber, Douglas) be launched. The planes launched, however, are TBF's (Torpedo Bomber, Grumman), which look nothing like a TBD.
Factual error: There are numerous shots of stock footage showing planes that weren't in service at the time of Midway, notably the Corsair, which didn't see carrier service until 1944, as well as the Helldiver, the Hellcat, etc.
Continuity mistake: The same Forrestal-class carrier (60's vintage with slanted decks and full radar suites) is used as the "Hiryu" and "Soryu"...one of which is simply the same film turned left-to-right, including the backwards hull number painted on the flight deck.
Deliberate mistake: The majority of the Japanese planes were actually done-over North American AT-6 Texans and their Navy counterpart, the SNJ.
Revealing mistake: Just before the Japanese planes were launched, you can see that the maintenance workers for the planes weren't moving. They were just statues.
Factual error: Some of the stock footage used in the battle sequences are actually just out-takes from the movie The Battle of Britain. Long shots showing dogfighting planes from that movie appear several times during Midway's combat scenes. In the torpedo attack on the Yorktown, one of the burning Japanese bombers is actually, on closer inspection, a German Heinkel, another borrowed shot from the B.O.B.