Other mistake: Murphy lands the helicopter on a railway line so an oncoming train will destroy it completely, and this happens exactly on cue with huge, dramatic explosions and flying debris. Apparently the train driver doesn't think this is important enough to interrupt his busy schedule - he doesn't stop the train. We do not hear brakes being applied - the wheels would make a noise like the sky coming down - and the train doesn't slow down at all - it just keeps on going.
Other mistake: The weather in L.A. sure is interesting, as well as the sunset/nightfall time. Near the end, before Frank Murphy notices the train and lands the helicopter, it is near sunset. The sky is still blue when we see a close-up of the train operator. By the time the latter notices the helicopter flying above the train, it is already night time. And just before landing on the rails, at night, the helicopter hovers a bit, and you can see that it is raining. When Frank exits the helicopter, it is a clear night. (01:43:00)
Other mistake: Look carefully at the helicopter during the strafing scenes; at one point, the gunfire is not coming from the Blue Thunder at all, but from a Bell helicopter at a distance. Also, when we see the Blue Thunder helicopter during the attack, the cannon does not seem to be pointing at its targeted shots, let alone turning.
Other mistake: His rank on the cap and the collars are different. Three rockers on the collars, two rockers on the cap.