The Newfoundland airport gets a visit from an American general wearing the insignia of General of The Army (5 stars). After Pershing retired in the 20s, no one held that rank until December 1944.
Aircraft are cleared for takeoffs and landings on various runways IE: 24, 25, 26, and 27 that don't exist. There is only a single runway at Gander and the two ends are named 03 & 21.
The cockpit side window is blanked out in the cockpit set and the example aircraft probably to simplify filming.
When an inspection was made by authorities at Gander Newfoundland, they spoke relating to the loss of Sir Frederick Banting. It was said attributed to (aircraft engine) "coolant loss." The engine in the Hudson he was a passenger in, was the Pratt & Whitney R-1830-55 Twin Wasp 18 cylinder air-cooled engine. Since it is air-cooled, there could be no "coolant loss" to attribute a loss of a flight to this reason.
The registration number on every Hudson aircraft seen is the same. The reason for this is that there was only one Hudson available to the film makers - it is actually an exhibit in the collection of the North American Aviation Museum in Gander.
In scenes that were supposed to be taking place in England, Canadian telephones can be seen everywhere. One character is seen using one with a coiled handset cord, which was not available in North America until after the war, and considerably later in the U.K.
The aircraft crews are using headphones with coiled cables. Coiled cables did not exist in 1940.
In one scene, Nathan is servicing a piece of equipment to which large transistors are attached. Transistor theory was not developed until 1947.
Newfoundland Airport manager is working on a piece of equipment which has three transistors visible. Transistors were not invented until 1947.
The DC-3 shown in the first episode was equipped with modern turboprops, and of course sounded nothing like a DC-3.