Shooting was completed on May 29, 1940, after which, Director Sir Alfred Hitchcock made a visit to England. He returned on July 3 with the word that the Germans were expected to start bombing at any time. Ben Hecht was hurriedly called in and wrote the tacked-on final scene set at a London radio station. It was filmed on July 5, and the real-life bombing started on July 10, 1940.

In a 1972 interview on The Dick Cavett Show (1968), Sir Alfred Hitchcock revealed that the plane crash scene was filmed by using footage shot from a stunt plane diving on the ocean, rear projected on rice paper in front of a cockpit set. Also, behind the rice paper were two chutes aimed at the cockpit's windshield connected to large tanks of water. With the press of a button at the right moment, water came crashing through the rice paper, into the plane simulating the plane crashing into the sea from the cockpit view.

When the plane crash sequence was shot, a special tub within the studio tank had to be built for Herbert Marshall, who couldn't swim because he only had one leg (he'd lost a leg in combat in World War I).

Albert Bassermann (who played the Dutch diplomat Van Meer) couldn't speak a word of English and learned all his lines phonetically.

When this movie was made, America was not part of World War II. At this time, several Hollywood studios were pro-American involvement in the war. This movie is one of several movies made during the late 1930s and early 1940s that represented pro-American intervention in the war. These movies include Confessions of a Nazi Spy (1939), The Mortal Storm (1940), A Yank in the R.A.F. (1941), Man Hunt (1941), and Sergeant York (1941).

Sir Alfred Hitchcock wanted either Barbara Stanwyck or Joan Fontaine for the female lead.

Robert Benchley was allowed to write his own lines.

DIRECTOR CAMEO (Sir Alfred Hitchcock): Early in the movie walking past Johnny Jones' hotel reading a newspaper.

Producer Walter Wanger and Director Sir Alfred Hitchcock clashed repeatedly during shooting. Wanger kept wanting to have the script re-written with every news story reporting changes in the European situation. Hitchcock, who hated making a movie without the script in absolutely final form before shooting began, pointed out that even if the movie were up-to-date at the time of shooting, it would be out of date by the time he finished post-production, and it was ready for release.

Johnny Jones/Huntley Haverstock was loosely based on real-life journalist Edward R. Murrow.

Sir Alfred Hitchcock's eccentric marriage proposal to Alma Reville was written into the script.

The only Sir Alfred Hitchcock movie for which Alfred Newman composed the music. Newman was named head of the Twentieth Century Fox Music Department the year that this movie was released, and until the record was broken by John Williams, remained the composer with the most Oscar nominations.

Producer Walter Wanger wanted to put a lot of political elements in this movie. But Sir Alfred Hitchcock tried to reduce the political elements as much as possible. Hitchcock felt that the movie would become dated since politics change from time to time. So Hitchcock tried to reduce mentioning Axis powers as much as possible.

Gary Cooper admitted to Sir Alfred Hitchcock that he'd made a mistake in turning down the lead.

The ending with Joel McCrea delivering a propaganda broadcast as bombs fall on London was written (by Ben Hecht) and shot after the rest of the movie was completed. It replaced a more sardonic ending in which Ffolliott (George Sanders) tells Haverstock (McCrea) how the enemies will likely cover up the incidents depicted in the main part of the movie.

According to Sir Alfred Hitchcock's interview with François Truffaut, Joseph Goebbels (Minister of Nazi Propaganda) enjoyed this movie very much.

It is not known what happened to the original ending of this movie, with Scott Ffolliott saying how the enemies will most likely cover up the whole thing.

Producer Walter Wagner described Sir Alfred Hitchcock as "fat, forty, and full of fire. I've seen him climb a ladder with unbelievable agility." In his treatment of the actors and actresses, Wanger did not notice Hitchcock as cruel or cold, but rather as "an alert and sensitive movie fan."

Producer Walter Wanger bought the rights to Vincent Sheean's political memoir "Personal History" (New York: Doubleday, 1935) for ten thousand dollars in 1935. After sixteen writers and five years, the script became the basis for this movie.

During the scripting stage, a second unit crew was sent to Europe to shoot establishing shots. Sir Alfred Hitchcock later told François Truffaut of the dangers of travel at that time: "this was in 1940, you see, and the cameraman who went over the first time from London to Amsterdam was torpedoed and lost all his equipment. He had to go over a second time." Location shots for the movie were sparse, however. For the most part, Hitchcock utilized elaborate and expensive sets. He always had a keen interest in set design, and would do rough sketches of ideas for his Art Directors.

Producer Walter Wagner challenged Director Sir Alfred Hitchcock's claim that he didn't even need to open his script during shooting. On the contrary, Wanger observed that Hitch's copy of the script was dog-eared before the first week of shooting was completed, and that it had "dialogue corrections on one side, sketches showing the composition of scenes, medium shots and close-ups on the other. In addition to having Art Directors prepare many sketches showing lights, shades, and suggested composition, Hitchcock will make as many as three hundred quick pencil sketches of his own to show the crew just how he wants scenes to look."

This was Sir Alfred Hitchcock's second American movie. He was hired out to Producer Walter Wanger by David O. Selznick, with whom he was contracted.

Sir Alfred Hitchcock originally wanted Joan Fontaine for the female lead. But David O. Selznick refused to loan her to Walter Wanger Productions for this movie.

The airliner in this movie is supposed to be a Clipper 314, which went into operation for the first time in June of 1939, carrying (also for the first time), passengers on a transatlantic flight. However, the plane was modified for filming purposes. The plane's logo says it is owned by fictional Transoceanic Airways, but the original flight was operated by Pan Am, and ran for three hundred seventy-five dollars one-way or six hundred seventy-five dollars round trip. In 2014 dollars, this would be equal to about four thousand dollars one-way, and twice that for round trip.

Director Sir Alfred Hitchcock wanted Gary Cooper for the lead instead of Joel McCrea, but Cooper wasn't interested in doing a thriller. He later regretted turning down the movie.

The music being used for by the Germans in the torture of Van Meer is Chick Webb's "Harlem Congo".

Producer Walter Wanger had the story in development for several years. Originally, it was about the Spanish Civil War, but that war ended too quickly, and therefore the story lost its relevance to audiences. Wanger insisted that the movie be politically up-to-date so re-writes were happening constantly throughout production. Ultimately, sixteen writers were involved in bringing the story to the screen.

While working on the script for this movie, Sir Alfred Hitchcock was extremely worried about his mother and other family members in England because of the upcoming war, so he applied the idea of "how immediately a war can start" in this movie.

The final cost of this movie was a then-staggering one and a half million dollars. The costs charged to the script alone, accounting for a total of sixteen writers, was two hundred fifty thousand dollars.

Sir Alfred Hitchcock took great interest in the scenes of the spy ring operating inside of a Dutch windmill. The creaky, atmospheric set was three-tiered and equipped with working gears, important to the plot as our hero's coat becomes entangled in them. Also built for the movie was an airplane equipped with four propeller motors, a wingspan of one hundred twenty feet, and an eighty-four-foot fuselage, most of which ended up in a giant studio tank.

According to press release information, more than six hundred laborers, electricians, plumbers, carpenters, and prop men, worked on the sets for this movie. A six hundred foot by one hundred twenty-five foot stage was used to re-create Waterloo Station for a few scenes, and even more extravagantly, an entire square in Amsterdam was constructed on a ten-acre site at a cost of two hundred thousand dollars. The scenes in the square, including the elaborate assassination and getaway shots, took place during a rainstorm, so the set had to be rigged with an elaborate drainage system.

Sir Alfred Hitchcock wanted Cary Grant for the lead role, but he was busy with Only Angels Have Wings (1939).

The film takes place from August 19 to September 5, 1939.

Although Germans enjoyed this movie when it was released in 1940, they weren't happy about the current ending written by Ben Hecht. Germans disliked the ending because it made it look like it was Germany who was attacking Great Britain, although it was Great Britain who declared war on Germany on September 3, 1939, and it was Great Britain who rejected the peace offers sent to them by National Socialist Germany under Adolf Hitler.

Working titles for this movie included "Personal History" and "Imposter".

The U.S. Copyright Office uses "Huntley Haverstock" as the example of a pseudonym.

Although Eduardo Ciannelli's name is spelled "Cianelli" in the comprehensive end credits, his name is correctly spelled in the opening credits.

Unlike the original ending of this movie, Sir Alfred Hitchcock wasn't involved in the scripting of the released ending. In the book "Encountering Directors" (1972) by Charles T. Samuels, Hitchcock revealed that the released ending was written by Producer Walter Wanger and Ben Hecht.

Producer Walter Wagner purchased the rights to Vincent Sheean's political memoir Personal History (1935) for ten thousand dollars. He decided to discard it after he declared several screenplays based on the book unsatisfactory.

Features Albert Bassermann's only Oscar nominated performance.

Clark Gable turned down the lead role.

On the plane, Jones and Ffolliot simultaneously scratch their noses in an identical manner, just before another passenger is asking for a drink.

This was one of two dozen Walter Wanger/Harry Sherman/Cinema Guild productions, originally released by United Artists, re-released theatrically in the 1940s by Masterpiece Productions, and ultimately sold by them for U.S. television syndication in 1950. The telecast of this title in New York City on Saturday, April 8, 1950 on WCBS (Channel 2) launched the series in New York City, and its widespread popularity spread quickly across the country. It first aired in Albuquerque on Tuesday, April 11, 1950 on KOB (Channel 4), in Philadelphia on Sunday, April 23, 1950 on WFIL (Channel 6), in Phoenix on Thursday, May 18, 1950 on KPHO (Channel 5), in Los Angeles on Sunday, June 18, 1950 on KTLA (Channel 5), in Cincinnati on Saturday, July 15, 1950 on WKRC (Channel 11), in Detroit on Sunday, July 30, 1950 on WXYZ (Channel 7), in Chicago on Sunday, August 13, 1950 on WENR (Channel 7), in Boston on Sunday, November 19, 1950 on WNAC (Channel 7), and in San Francisco on Saturday, December 9, 1950 on KGO (Channel 7).

In the scene where Joel McCrea climbs out of a window of the windmill and then into another, just inside the window he climbs in, on the right, the wooden boards, two pegs and their shadows create a profile image of Adolf Hitler.

The scene in which a German destroyer shoots down a British airliner at the outset of World War II may have been influenced by the real-life sinking of the S.S. Athenia, the first British passenger ship to have been sunk by U-boats. By coincidence, one of the survivors of the Athenia sinking was Judith Evelyn, who appeared in Sir Alfred Hitchcock's Rear Window (1954) and two episodes of Alfred Hitchcock Presents (1955). By a further coincidence, Evelyn's father was amongst the Athenia passengers killed, parallelling the fate of the Fishers in this movie (Carol survives, her father Stephen does not).