The parachutes used by the troopers are equipped with anti-inversion nets. They are around the skirt of the canopy to prevent partial malfunctions. The nets were not developed until the mid 1970s, shortly before the movie was filmed.
There is a German tank featured in several scenes. This tank is actually a German-made, post-war tank named "Leopard I" with a few modifications to look like a German Panzer V Panther tank of the World War II era. Given that the Leopard I is actually an offspring/based on the Panzer V this is a good choice.
In the "meeting of the generals" scene early in the movie, a cold-war-era map of Europe and the Middle East can be seen. Clearly visible is the German-Polish border at the post-WW2 Oder-Neisse line (though no inner-German border), Austria separated from Germany, a post-WW2 Czechoslovakia, the West Bank occupied by Jordan, and Gaza strip occupied by Egypt.
When Gen. Bittrich sees all the paratroopers coming down, here says something like "Just once to have such power in my hands." However, in the C. Ryan's book it is German paratrooper expert Gen. Student that makes that statement.
When the boats finally arrive to cross the river at Nijmegen bridge, there is water in them, even though they've been transported for days in trucks in rain-free weather. (Probably a result of previous takes.)
At the beginning of the film when the American and British officers are talking, the general's epaulets are on top of his coat collar. A minute later, as the general walks around the table, the epaulets are under his coat collar.
The subtitles when Field Marshall Rundstedt is speculating between General Patton and Field Marshall Montgomery near the beginning of the film once misspell "Patton" as "Patten". Later usages correctly spell "Patton".
When von Rundstedt is deciding where to send his armoured reserves in order to rest them before meeting the expected attack by Patton rather than Montgomery he decides to send them to Arnhem. The map counter which is moved clearly shows "II SS Panzer Div (division)" when the correct name of the unit at Arnhem was the II SS Panzer Corps (consisting of the 9th and 10th SS Panzer Divisions). The 2nd SS Panzer Division at that time was fighting on the Eastern Front.
As the first British paratroopers are assembling, there are wide angle shots of activity. Most of the paratroopers are carrying the correct rifles, machine pistols or other weapons, but a few can be spotted carrying American M1 Garand rifles that were rarely used by British or Commonwealth forces. Later in the movie, as the tide turns and the British paratroopers have surrendered, German soldiers crossing a small foot bridge to the British command post can be briefly seen carrying M1s as well. M1s were issued to a small percentage of Commonwealth airborne troopers to increase the rifle fire-power of squads. Photos of Canadian airborne troops verify this.
When Ludwig is speaking to a subordinate about blowing the bridge about to be assaulted by the 82nd, the subordinate refers to a "Hauptmann", the German word for captain. In the SS, the rank would be "Hauptsturmführer." Likewise, when he answers Ludwig, he calls him "General". Ludwig is listed in the cast as a Major General, but the equivalent SS rank would have been Brigadeführer. In the film, Ludwig's collar tab has 3 oak leafs and 1 pip which stands for Gruppenführer (General Lieutenant), even though his rank is that of a Brigadeführer.
Brigadier General James Gavin's (Ryan O'Neal) insignia of rank is incorrectly displayed on his "Ike" jacket. Brigadier Generals wear the star positioned at the middle of the epaulets rather than at the outer edge as do officers in the grade of Lieutenants through Colonel.
In the film, a group of British paratroops kill or disperse the resting crew of a German tank outside the row house where General Urquhart and his aide are hiding, thus allowing him to return to his headquarters. In reality, Urquhart and his aide just hid and waited for the German tank to move on, which it did without any gun play or contact with the British paratroops.
During shots of Nijmegen, the tower of the Sint Stevenschurch is standing tall. In fact the tower was destroyed by an American bombing off Nijmegen in February 1944. It was not put back on the church until the late sixties. The opening of the renewed tower was in 1969.
After the initial attempt by XXX Corps to break out, there is a scene of a wrecked M24 Chaffee being pushed of the road. There is also a burning M10 Tank destroyer among the wrecks. Not only are these vehicles not visible in the initial advance or fighting scenes, but neither were used by the British Army. The M10 might pass for a 17Pdr gunned Achillies.
The bomb placed as shown would never collapse the entire bridge, because although it's directly under the road surface, it's 80 ft under the apex of the steel arch, the strongest part of the structure, which would remain intact after the bomb goes off. The bomb would have virtually no effect. The best the explosives could achieve where they're shown would be to disrupt the road surface.
Operation Market Garden began on Sunday, 17 Sept. 1944; in the movie, Gen. Browning correctly refers to a Sunday departure in the initial briefing, and later we see a church service disrupted by the aircraft passing overhead. But on the morning of the departure, we see on Col. Frost's bedside table a calendar with all the days crossed off until the 17th... which is a Tuesday on that calendar. Furthermore, the calendar clearly shows a 31-day month, obviously not September.
In the opening monologue, the unidentified woman states that in 1944, before D-Day, the Second World War was in its fifth year and "still going Hitler's way". In reality, long before D-Day Germany had already suffered crushing defeats on the Eastern Front at the hands of the Soviet Union, at Stalingrad in the winter of 1943, and at Kursk in the summer of 1943. It had also been kicked out of North Africa by the Western Allies. Thus, by mid-1943 Hitler and Nazi Germany were already well on their way to ultimate defeat.
When a damaged Allied cargo plane "crashes" behind some trees near Maj. Gen. Urquhart and his troops, the plane can be seen pulling up and flying away just behind the fireball marking its supposed impact point.
When the English soldiers are are standing and yelling to the supply drop aeroplanes a damaged plane flies past with an engine out and crashes soon after, but the plane can be seen flying away from the left side of the explosion
As the Dutch Advisor Harry yells at Gen. Gavin after landing "you all right?" Several men in the background are carrying K98 German rifles instead of M-1 Garands, could be a war trophy but they carry no other rifle, and they just landed and wouldn't have time to get pick one up.