Revealing mistake: During the big chase scene when the tram is out of control as it hits the last car and blows up you can see rubber tires on it, specially added to let it go on tarmac.
Factual error: When the Seals team swim towards the rock they are aided by microsubs, which all have headlights that are on. The light would be reflected at the surface and would be detected in the blackness that is all around. They do not need lights, all they need is modern technology to direct the subs, which they have. Details like this would have been determined during the planning of this operation, and fully trained Navy SEALS would know better either way.
Continuity mistake: When Sean Connery is in the interrogation room when there's all the commotion and everybody leaves, before he breaks the glass, you can see a yellow mark where he scores and then punches the glass.
Factual error: When Goodspeed fires the rocket at Captain Darrow, the rocket back blast would've killed Goodspeed. Despite the fact that he ducks to try and avoid it, the flames would've completely enveloped the room, killing if not serious injuring anything inside.
Continuity mistake: When Goodspeed tries to call his girlfriend and tell her not to come to San Francisco, she tells him she is going and hangs up the phone on him. The phone and her are in front of a window with a skyline in the background. Goodspeed lived and worked in Washington DC, but the skyline in the window is that of Los Angeles. You can recognize LA's tallest building in the background, Library Tower.
Factual error: When the pilots are being briefed about the mission to bomb Alcatraz, they are in the front of the hangar, and an F/A-18 is between them and the camera. There is an AIM-9 missile on the left wingtip of the jet, but no dome cover. AIM-9s always have a protective cover over the seeker head of the missile to keep the eye from drooping when power is off the jet.
Continuity mistake: After the shower scene, the bad marines are searching for Mason and Goodspeed. When the 2nd grenade explodes and the 2 are running away, Mason is in front but when the two dive into the water and the shot changes to from beneath the water Mason has somehow managed to get behind and on the other side of Goodspeed.
Continuity mistake: When Mason and Goodspeed make their way to the morgue, Mason disposes of a marine with his straight-as-an-arrow knife throw. Watch very carefully, as there is a split second during which the marine appears to sustain the impact of the knife, and we hear the sound of it. But there is no knife to be seen until the next shot, where he is gasping for breath and trying to pull the knife out of his neck.
Continuity mistake: When Goodspeed is on the roof of the lighthouse with the last pearl configuration of poison gas, one of the 'pearls' drops off the bottom. As he chases it across the roof, from the front shot he has his right hand outstretched. As he dives to grab at it, the shot switches to the side and it is his left hand that grabs the 'pearl'. The shot then immediately switches to a close up of his face and you can again see his right arm outstretched. (01:54:30)
Continuity mistake: In the hotel suite scene, when Mason has thrown Womack outside, Godspeed is aiming him a gun. At the beginning you can see it's a Beretta 92 but when he says "please, don't" and the shot changes, the gun becomes a Colt 45. Then the shot switches again and Godspeed is again holding a Beretta 92.
Factual error: During the car chase scene the cable car used was not from the California line (despite the signage on the trolley saying it was) as it had open seats and a driver area at only one end. This type of trolley is used on the Powell Mason line where there are turntables at the end of the line. California line has open seats and driving levers at both ends, so it can change direction without a turntable.
Visible crew/equipment: When Sean Connery is fighting the guy whose legs are on fire, watch Sean's stunt double. There's a rope and a metal safety harness holding him steady.
Visible crew/equipment: During the Humvee chase, right after the FBI car is on its wheels, you see someone wearing a helmet come out the car. There were no police bikes in the chase so that means it was a stuntman who got out.
Continuity mistake: The deadline is at noon, but when Goodspeed is running to the lower lighthouse after the shootout with Hummel's guys, the skyline is either dawn or dusk.
Revealing mistake: In the shower room massacre scene, you can see a bullet casing when they show one of the dying Navy SEALS really close-up. If you look carefully, the end of the casing is crimped, which is what a blank round's casing looks like. A real bullet casing would not be crimped at the end.
Other mistake: When Cage throws up in the lavatory, the sink is empty before and after.
Continuity mistake: After the underground shootout involving three of Ed Harris' men (as Mason and Goodspeed escape the morgue), the dead man in the cable car visibly blinks upon close-up.
Continuity mistake: When the SEAL team is onboard "Raider one" the pilot says "we're going dark" and SEAL commander gives them order to turn nightvision on. However, when camera shows the chopper from outside, there is a beacon light flashing in its tail. Trained Navy SEALS would never overlook this detail under any circumstances.
Continuity mistake: After the shower room scene where everyone's killed, Hummel and his men are checking out the bodies. They find a soldier who is still alive. Hummel then speaks in the camera on the marines left soldier. The film then cuts to the command center in San Fransisco. A man looking at a screen points at it and says "Look at this." In the shot, as he points to the screen you can clearly see it as being a radar screen, but in the next shot it turns to the screen with all the marines' camera's views on it.
Continuity mistake: When Ranger Bob welcomes the tourists to Broadway, both his socks are pulled up. A moment later, one sock is pulled up all the way, and the other only partway.
Chosen answer: Alcatraz is small enough and out in the middle of the bay that any lookout in a high point could see and hear a chopper, no matter where it approached from. The idea of the decoys was to split any enemy fire received. The whole insertion of SEALS was absurd, in a real situation like that, the SEALS would have been inserted by submarine or used dive motors to pull themselves to the island.
Grumpy Scot