The Luftwaffe did not start painting fighter aircraft nose cones yellow until later in 1940. However Christopher Nolan has admitted this was done deliberately to make the German aircraft easier to identify by the audience.
There are two instances when the German Heinkel He-111 comes under attack by a British Supermarine Spitfire. Both times, the Heinkel sounds like it fires cannons in its defense. The Heinkel He-111 H-3 variant, the one used during the time period, did not have cannons as defensive armament. It was armed with MG 17 Machine Guns as defensive armament.
The standard ammunition load for a British Fighter in early World War 2 was the Caliber .303 round with eight (*) wing mounted machine guns. The rounds were in arranged with ball, tracer, incendiary, and armor piercing projectiles in-dispersed in the ammunition loading. Of special note was the B4/B4Z incendiary round that had soldered holes (over a phosphorus core) in the projectile that when fired melted from the friction of the projectile leaving the barrel which left a visible smoke trail as the bullet flew through the air. This is evident in the actual combat footage used in earlier films ("Battle of Britain") involving Spitifres or Hurricanes where British aircraft fired their machine guns, a line of spiraling smoke trails reach out towards their target. This type of ammunition was an aid to marksmanship. Later in the war the British moved to use tracer ammunition which leaves a bright colored trace in the air.
The film shows several vehicles of a later second world war type. Understandably, period vehicles are difficult to come by, the vast majority having been either destroyed, scrapped, or simply rotted away at the time.
The Luftwaffe (German Air Force) fighter aircraft used during the time of the events at Dunkirk would most likely be the Messerschmitt Bf 109E. The plane used in the movie is a Hispano Aviación HA-1112, which is a Spanish variant of the Bf-109 introduced after the war, powered by the Rolls-Royce Merlin engine, like the Spitfire. HA-1112 are commonly used as substitutes for Bf 109s as they are almost identical in appearance save for the HA-1112's less-streamlined cowling.
Some shots of the breakwater construction under the wooden pier walkway clearly show that the breakwater is made of precast concrete Dolos (giant concrete versions of toy jacks) that were not invented until 1963 to combat beach erosion.
In the background of the scenes on the beach giant "modern" post 1970 container cranes can be clearly seen. These giant walkers were developed in the 1980s to facilitate removal of shipping containers and did not exist in 1940. They appear in the background of many scenes including the climatic final scene.
During a high shot of Weymouth, the current Pavilion can be seen. This is actually The rebuilt Pavilion after the Ritz Theatre burnt down in the 1950s. Also, the ex-Condor Ferries terminal can clearly be seen, still painted in their corporate colours.
One of the authentic Little Ships that appear in the film is clearly named 'RIIS I.' However, at the real Dunkirk evacuation, this boat was appeared with the name 'White Heather;' she was only renamed 'RIIS I' in 1949, 9 years after Dunkirk and 4 years after the war.
In the grounded fishing boat, the soldiers have a lengthy discussion who to sacrifice in order to aweigh. During the argument several cubic meters of water floods though the bullet holes, weighing more than all men combined and making the debate futile.
The film focuses on some soldiers jumping the queue, when one of the noted characteristics of the Dunkirk evacuation is how extremely well disciplined and ordered the soldiers were in queuing for the ships.
The Royal Navy Officers conducting the boat requisitions early in the film are wearing the incorrect cap badges. Instead of the cap badge worn by officers to signify a commission, they wear that of a Petty Officer, a non-commissioned rank.
The beach section of the movie takes place over a week, whereas the air section of the movie takes place over an hour. The craters shown earlier on the beach would have been filled in by sand when the tide came in over the days leading up to the pilot having to land his spitfire, so it wouldn't necessarily still have the craters when this scene happened.
After Farrier (played by Tom Hardy) sets his plane on fire with a flare gun to prevent the Germans from capturing the technology, and the plane slowly burns to the ground, the propeller of the aircraft is attached only to a long shaft in place of where the engine would be. There is no engine in the plane/prop. Even in a fire, the solid metal engine block would be present and not melt.
Mr. Dawson's 'Moonstone' is portrayed as returning from Dunkirk to Weymouth in Dorset. That's 250 miles - which at a cruising speed of 7 knots would take more than 2 days flat out. The real small boats went to places such as Ramsgate.
Photographs and video footage taken of the beaches at Dunkirk after the evacuation show the beaches being littered with abandoned vehicles, equipment, wreckage, and bodies. The beaches in the film remain relatively clean throughout the film.
The Mk 1 Spitfires portrayed had a total fuel capacity of 85 imperial gallons. This was held in two tanks - one above the other. The top tank emptied into the bottom tank till it was used up. The fuel gauge the pilots are checking was only capable of measuring the bottom tank which held 37 gallons. Therefore it would not be possible for the pilots to determine they had 50 galls of fuel remaining.
During the aerial combat scenes, the British pilots always fire at the enemy planes when their targets are right in the centre of their gun sights, regardless of the direction their targets are moving. Realistically, they would have had to "lead" their targets, i.e. aim at a point in front of the enemy planes, to compensate for the time it takes the bullets to travel the distance.
Before a ditching or forced landing, a pilot would have been trained to open the canopy to prevent it from jamming because of the impact forces (incidentally, in many cases, pilots taking off from aircraft carriers even left the canopy open just in case they ditched immediately after lifting off). Not only does this not happen in the movie but, in one case, the pilot even opens the canopy and, inexplicably, closes it back before touching down (actually leaves it ajar one inch or two). Predictably, in the second case, the canopy jams, nearly causing the pilot to drown.
Further, in this second case, the pilot waves through the opening. However, there would not have been enough of an opening for him to squeeze his forearm through.
The Spitfire pilots expend over 70 seconds of ammunition during the course of their one hour mission. In 1940, pilots would need to have been far more frugal: Spitfires would need to rearm after only 15-20 seconds.
Following the trial docking of the first ship, the moles were initially used with a number of ships docked at once. This was reduced when they became a greater target. The majority of soldiers were evacuated by large ship, including large civilian vessels (which shouldn't detract from the achievement of the small ships alongside).
The film shows very few vehicles, when the British Expeditionary Force was one of the first armies to be fully mechanised. The BEF lost around 600 tanks, 64,000 vehicles and 20,000 motorbikes, many of which would have been in Dunkirk.
When Thommy is going through Dunkirk town with fellow British soldiers at the beginning, the town is quite intact. In actuality it would have been heavily damaged from bombing raids by the Luftwaffe and German Artillery.
The movie uses silence to create tension, where Dunkirk was actually extremely noisy due to the continual attacks on both the men, and the port of Dunkirk to keep it out of action. Most soldiers had sore throats from having to shout to be heard.
Mr Dawson's boat is based at Weymouth Harbour. On the upper loading bay the tracks for the dock cranes are visible on the floor but there are no dock cranes. These would have been there in 1940 and were actually removed in the 1970s-80s.
The sidings outside Woking station are inside the town where there are buildings that were around before 1940. The film shows the sidings in the middle of the country that doesn't resemble the landscape of Surrey where Woking is. The depiction of Woking station also shows a red sign in the more modern British Rail typeface, not introduced until after 1965.
A minesweeper marked 'J22' appears during one of the evacuation sequences in the latter portion of the film. While there was really a Royal Navy minesweeper operational at the time with this pennant number, it did not participate in the Dunkirk evacuation.
Once the Dutch fishing boat floats on water, the film presents that bullets penetrate the ship's hull even at a depth where water leakage was uncontrollable. While grounded, it is likely that bullets would penetrate ship's hull. But once floating, it is unlikely that the common German rounds would penetrate the hull because of the water resistance.
In a scene showing the right hand side of the Spitfires cockpit there's a bit of fluff attached to one of the rivets , then the fluff is gone, then a shot of the left side of the Spitfire and the same piece of fluff is there.
Throughout the movie the British Spitfire fighters are shown with a rectangular "radiator" beneath their right wing. However, late in the film, right around the time when Tom Hardy's character ("Farrier") switches to his auxiliary fuel tank, there is a brief external view of the plane flying, where this "radiator" appears to be under the left hand wing. It is possible that the film was inverted in that clip.
A French character is shown having dressed in British uniform to escape France. In reality he would not have needed to, as French troops would be embarking at the second mole to re-deploy to the South, and a decree by Winston Churchill later in the evacuation ordered an equal number of French soldiers be brought back to England at the risk of British soldiers being left behind. Ultimately, of the 338,000 soldiers evacuated from Dunkirk around 123,000 were French. However, a 'little ship' crew member recalls seeing French soldiers taking the uniforms off of dead British soldiers and wearing them, hoping for evacuation.
During the movie the beach is a cratered landscape, caused by continuous bombing. In the end sequence, when Farrier floats over the beach trying to land, the surface is completely smooth. However, many areas of the Dunkirk beaches were relatively flat and made of hard-packed sand. It has been recorded that pilots found it was an ideal landing strip, and some RAF aircraft did land on the beaches.
When the Spitfire was burning, the engine cowling had burnt away but there was no engine. In one of the last scenes, the propeller was suspended by a pole that came out the engine bay, where the engine's output shaft should have been.
As the Spitfire glides over the Dunkirk Beach a number of the houses in the background were definitely modern, some with aluminum facades. The architecture for many of the homes appears to be late 20th century.
Many of the shots of Tom Hardy in the Spitfire cockpit were shot in a different two seat prop aircraft (visible in a youtube video - search Dunkirk Lee on Solent) which was been adapted to resemble the rear of a Spitfire and it's distinctive tail. The revealing element is the extended tail wheel, which is longer than that on the Spitfire.
In some of the transport ships scenes and one or two scenes on the pier at 'The Mole' the end of the barrel on several rifles can be seen to be solid. Holes at the end of the barrel bore should be seen.