Slama picks up Vojtisek at crash landing site an they both head to England over the channel. These two sequences are shot with a different aircraft.
The Czech RAF sergeants are often saluted and addressed as "sir".
In the language teaching scenes there are some model airplanes hung up from the ceiling. Two of these are the Lockheed P-38 Lightning and the TBF Avenger. Both of these airplanes were not built and put into service until long after America came into the war and this scene takes place in 1940.
The RAF-commissioned officer conducting the life raft training is shown wearing "shoulder flashes" with an embroidered eagle. These were not worn by commissioned officers, only by Warrant Officers and below.
A fighter aircraft could not explode in the air after being shot at.
The machine guns aboard the British aeroplanes fire at around 600 rounds per minute. The Browning Mark II* machine guns used by British aeroplanes fired 1,150 rounds a minute.
During training on the "bicycle Spitfires" and later during actual missions, the pilots fly in the "finger four" formation. This wasn't officially used until at least two years after the depicted events. Experienced pilots had been experimenting with it, but it would not have been used by trainees.
In one scene set during the 1939 sequence in Czechoslovakia there is a reference to Hitler and his mistress Eva Braun. Braun's very existence, let alone her status as Hitler's mistress, was not widely known to the public until the announcement of their marriage just prior to their dual suicide in 1945.
The Spitfires shown as taking part in the Battle of Britain (1940) have four-blade propellers, but the Spitfires used before 1942 had only three-blade propellers.
When Susan is explaining to Karel that her husband is serving in the Royal Navy but has been missing at sea for a year, the ship below his photograph is an American Iowa class battleship. The first ship of this class (USS Iowa, BB-61) was not commissioned until February of 1943, long after the period of the film, and they never served in Royal Navy.
A significant number of the Spitfires shown are later marks than would have been used in 1940, as is evidenced by their larger (and subtly differently shaped) vertical stabilizers and two underwing radiators. (Mark I and Mark II Spitfires would have had only one underwing radiator under the starboard wing, supplemented by a much smaller oil cooler under the port wing.) Also, the scenes in which Me109's appear show aircraft with unusually large chin cowling, indicating that they were probably made in Spain under license after the war (and equipped with something other than the period-correct Daimler-Benz engine that an Me109 would have had in 1940).