In Kurtz's dossier the cover letter in one section is a commendation to Col Kurtz for arranging a fly-by of Cobra gunships for a celebration or parade on "30 Aug 65." The first prototype of the Cobra gunship didn't fly until 7 Sep 65.
Before the Playboy/USO show where the crew is trying buy fuel from the quartermaster, the Playmate centerfolds hanging on the wall behind him are from the mid '70s, rather than the late '60s. The centerfold on the far right is Cynthia Wood, 1974 Playmate of the Year, who soon appears in the film during the USO show.
On the cover letter to Kurtz's dossier package, it is indicated he graduated West Point in 1946; 49-50 he was attending Harvard (completing his Masters degree); 50-51 he was assigned in Seoul, and 52-53 he was assigned to West Point ("..Teaches courses in American..."). However, on the last page that we see in the dossier (the form sheet, with the Dept. of Defense seal as the watermark) it is listed that he was at West Point 1941-45, and at Oxford University 50-52.
During Willard's briefing in Nha Trang, every time someone mentions the name "Kurtz" on the soundtrack, on screen they are mouthing "Lieghley", the original name of Col. Kurtz's character in the script during the early part of the shooting.
When Captain Willard first meets Colonel Kilgore, they exchange salutes while they are still in a combat zone. It is usually military protocol not to salute in a combat zone. Saluting would show a possible sniper who the commanding officer is. (e.g. in Forrest Gump (1994) Lt. Dan correctly instructed Gump and Bubba not to salute him in the field.)
When Bill Kilgore asks about the 6 foot peak, he asks Mike about the point. Earlier, Kilgore introduces Lance Johnson to Johnny from Malibu and Mike from San Diego and Johnny is really the one he asks, not Mike.
When Willard is looking through the dossier at the times that Kurtz was denied a transfer to Special Forces ("jump school"), the reason for disapproval is written: "The Army feels, all maters of age and fitness aside..."; "matters" is misspelled.
When Willard is first shown a photo of Col. Kurtz the name tag on his uniform reads "Leighley". When Willard looks at the photo a second time, the name tag reads "Kurtz". (This is due to the fact the character's name was changed from Kurtz to Leighley and then back to Kurtz during the film's production.)
After the canopy of the boat is destroyed and is replaced by giant leaves, the canopy reappears while they are at the bridge. In subsequent shots after, the canopy is gone again and replaced by the leaves.
In the opening montage two different ceiling fans are seen. One is light colored with a louvered housing on the motor. The other is black with no visible motor housing, and is spinning counterclockwise.
When Johnson is painting the Playmate of the Year's face, you see a shot of her forehead already painted black. About a minute later, her forehead is clean and he is applying the black makeup, seemingly for the first time.
When the PBR leaves the Do Lung bridge, it has a radar dome. When they cut to the next river day scene, it doesn't. then, when chef hands out the mail, it does. For the rest of the trip, it's not there. Captain Willard even sits on where it should be when they reach Kurtz's lair.
During the helicopter attack scene, an American soldier gets wounded in the courtyard. Shortly afterward you see the courtyard designated by the yellow smoke of a smoke grenade. However, the next shot is of the courtyard and there is no yellow smoke yet and you can see a soldier toss the smoke grenade onto the ground. It just barely ignites before the scene cuts to the next shot.
In addition to Willard's Band aid on his cheek appearing out of nowhere, if you watch the laceration on his cheek, it is more healed early in the movie, and more raw later in the movie. Indeed, Martin Sheen has a scar at that location at the beginning of the movie in the hotel or apartment when the movie opens.
LTC Kilgore's helicopter wasn't carrying surfboards. He sent his helicopter with the injured child and his mother. His helicopter carried rocket pods which weren't present when it left (could have been released after the pods were emptied). The surfboards were on a helicopter to the left of Kilgore's.
On the boat after the tiger, there is one quick shot, in which Clean is dressed completely differently--in a button-down fatigue shirt, not the bulky sleeveless flak jacket and t-shirt he is wearing in the rest of the scene.
When Roxanne Sarrault smokes a cigar during dinner, when only she, her father and Willard are present at the table. At the same time we see the arm of the man who earlier sat next to her, but in the next shot he is gone again.
When Willard and his crew meet Kilgore and the cavalry for the first time and walk onto the beach, long shadows (caused by the setting sun) of the camera and its crew are visible where the soldiers walk.
When a helicopter is traveling over the hills in the distance after Willard's mission briefing from the high rankings, in the bottom right of the shot you can make out the shadow of another helicopter traveling away from Willard's one. This is possibly a camera helicopter.
The maximum gross weight of a Huey helicopter is 10,500 pounds. It would be impossible for such an aircraft to lift a Patrol Boat, Riverine (PBR) which weighs anywhere between 15,000 and 19,000 pounds.
During the air-strike on the village, Kilgore calls for "20 mike-mike Vulcan" to be shot from the Huey gunship. The UH-1 Huey does not carry an M-61A1 20mm Vulcan cannon. The Gatling gun which that is shown being shot is a Minigun, which shoots a 7.62mm NATO (.308 cal. Winchester) cartridge.
In the scene the morning after the Do Long bridge incident, following Lance's popping smoke ("purple haze," he calls it), Clean is shown about to listen to his tape and an M-60 is shown on the left with linked ammo dangling and draped over the boat's side panel. However, the ammo rounds are clearly blanks with the characteristic blunt bottle-nose tips, not real rounds.
While Col. Kilgore's hat and decoration changes, earlier having oak leaves and crossed sabers (as would be seen with having different hats for when one became sweat soaked in Vietnam) and later just larger crossed sabers; it is most noticeable after he lands following the napalm use. It is seen earlier with the hat cords for a warrant officer which are silver/black instead of gold/black for officers of Lt. Col rank. (This is only readily-visible in the "Redux" restored version.) In one scene, he is shown with the hat acorns near-joined together on the brim as worn in the WW I M1903 campaign hat similar to that worn by highway patrolmen. Military hat cords of a cavalryman would never have been permitted to do this.
When Willard is showing a map to LTC Kilgore on the night of the Huey attack, it is impossible for both to see the map because of the light angle caused by the fire. The map must have been completely dark from the actors' point of view.
Capt Willard's audio narration says this about Lt Col Kilgore's unit: "The First of the Ninth was an old Cavalry division." But in military shorthand, 'First' would indicate the 1st Squadron (Battalion), and 'Ninth' would indicate the 9th Regiment. Neither of these is a division, which is a higher echelon organization.
The Viet Cong's tracer bullets, seen quite often throughout the film, notably when the PT boat is "sprayed" with enemy fire, appear to be red in color. In reality, the Viet Cong used green tracer ammunition while the American's used red tracer ammunition.
One of the documents in Kurtz's dossier being read by Willard is an official commendation dated January 24, 1964, which is a civilian date format. The date should have been typed in military format, which would be either 24 January 1964 or 24 Jan 64.
When the Bell Huey lands on the beach, the motto written on the front is "Death From Above" which actually was the motto of the 505th regiment of the 82nd Airborne "All American" Division, not the motto of the 9th Cavalry Regiment, which is actually "We Can, We Will".
After the helicopter carrying the wounded child leaves, Lance's clothing has changed from his Army fatigues to a pair of shorts (this is because of a cut scene in which Kilgore gives him a pair of shorts to surf in. The scene was restored in the Redux edition.)
"One of the officers who briefs Capt Willard on his mission to find Col Kurtz is a full colonel named Lucas (Harrison Ford). At about 35 years of age, Lucas/Ford would have been too young to have held such a high rank during the Vietnam War (although this did happen in World War II)." Since we do not know Lucas's age and given that his career would have spanned two wars (Korea and Vietnam) in which promotions are accelerated, it's entirely possible that a man in his late 30s would achieve the rank of colonel.
As Willard flips through Kurtz's dossier, the voiceover says, "Third generation West Point, top of his class" while the dossier clearly reads, "Graduates West Point; second in class." Second is still reasonably considered "top of the class."
Kilgore's helicopter attack scene, according to the dialogue between him and Willard the previous night, states that the attack will take place at dawn. Yet most of the scene itself was clearly filmed at high noon.
When Kilgore calls for the soldier to start The Ride of the Valkyries, the soldier starts the reel-to-reel tape. Unfortunately, none of the tape actually touches a playback head. Instead the tape is wound underneath a tension bar and on to the take-up reel.
In the Redux version, there is a scene where Capt Willard is walking through a heavy downpour at the Playmate/Medevac helicopter site. His M16 is slung over his shoulder with the muzzle pointing upward. This allows rain to enter the rifle's mechanism, resulting in rust and and eventual jamming. Real combat troops carry their rifles with the muzzles down while in the rain to prevent this from happening.
According to the identity cards Willard thumbed through, one of the Vietnamese spies Kurtz assassinated in November 1968 was Vo Van Sau, born on 30 September 1947. However Vo's photograph is of a balding man who certainly looks no younger than thirty.
During Clean's funeral, the Chief folds the tattered American flag from the stars end to the stripes end. Even a Cub Scout knows you fold the flag from stripes to stars, leaving the blue field on the outside. A Navy Chief Petty Officer would certainly know this. This was almost certainly intentional on the director's part; it may symbolize the chief's disaffection with the war, or at least with his mission (similar to flying a flag upside-down as a sign of distress).