In one scene, the pilot of a biplane shoots down a more advanced single-seater enemy bomber whom he stealthily caught from behind. The biplane pilot also happens to be a doctor. He lands his own plane and pulls the enemy pilot from the wreckage. Dwelling on the madness of war they hurry to put on their masks since poison gas is leaking from the bombs in the wreckage. A little girl joins them and the enemy pilot insists she wear his mask. The biplane pilot then hurries to get the girl and himself out of the danger zone, pausing to leave the enemy pilot a gun. The man dwells on the irony that he may have gassed the little girl's whole family and yet he has saved her. He then commits suicide.
The war lasts for decades, long enough for the remaining survivors to have forgotten the reasons for it in the first place. Strategic bombing is so successful that civilisation on both sides is totally devastated. Humanity falls into a new Dark Age where the technology level is reduced to that of medieval times, symbolised with a car being drawn like a cart by a horse. There is even a medieval-type plague sweeping through the land, known as "the wandering sickness", which was spread by the enemy, who dropped bombs containing the virus from their few remaining aircraft.
In 1970, Everytown is run by a local warlord called Rudolf, a.k.a 'The Boss' or 'The Chief' (played by Ralph Richardson), who is at constant war with the "Hill People" and obsessed with repairing the remaining biplanes and capturing coal mines in order to convert the coal to petroleum for the aircraft. The Chief consolidated his power over Everytown after having eradicated "the wandering sickness" by shooting all those infected with the disease.
One day, a futuristic aeroplane lands outside the town. The Chief and the townspeople are incredulous when the pilot John Cabal (played by Raymond Massey) proclaims that the last surviving band of scientists have formed a society known as 'Wings over the World'. They are building a civilisation, based in Basra, Iraq, that has renounced war and outlawed independent nation-states. The Chief resists by making the pilot his prisoner, but the Chief's mechanic (whom he was using to repair biplanes from the war) escapes to Basra in a plane he was testing, and alerts Cabal's scientist friends to his capture.
Wings Over the World mount an attack upon Everytown, and the skies fill with futuristic aeroplanes and bomb the town with a sleeping gas known as "the Gas of Peace" to pacify it. The Chief orders his few biplanes to attack them, but they are all shot down.
The populace of Everytown awakens shortly thereafter, to find it occupied by the Airmen, and their Chief dead — presumably from a heart attack brought on by the belief that the gas was deadly, or maybe by suicide in the face of defeat. The mechanic who had escaped to bring the Airmen comments on the Chief's death, to which Cabal replies, "Yes, dead. And his world with him - and so the New World begins!".
A montage sequence follows showing decades of technological progress and human achievement, beginning with Cabal explaining the plans of the Global Conquest by the Airmen of Wings Over the World ("First this zone, then that!").
By 2036, mankind lives in underground cities. Everytown is one of them (the only one shown, with no information given on any others - or if there even are others), and the first flight to the Moon is about to be launched from a space gun nearby. However, Luddites among the population fear this new technology, led by a sculptor who claims mankind needs a "rest" from further technological development, and that shooting people into the cold of space is not "natural". They start a riot, trying to destroy the space gun before it can be fired. The head scientist Cabal (the great grandson of the pilot in the previous section of the film, and also played by Massey) explains that the crowds are misguided and that technology has in fact saved humanity. He launches the space ship with his daughter and the daughter's boyfriend as the crew, and the blast from the launch knocks the crowd back.
The film ends with Massey's character delivering a speech to the idea of Progress and humanity's quest for knowledge, claiming that "if Man is merely an Animal then he must fight for every scrap of happiness he can, but if he is something more, then he must strive for more — the Universe or nothing - which shall it be?"
In fact, Wells ultimately had no control over the finished product, with the result that many scenes, although shot, were either truncated or not included in the finished film. The rough-cut reputedly ran to 130 minutes; the version submitted to the British Board of Film Censors was 117m 13s; it was released as 108m 40s (later cut to 98m 06s) in the UK, and 96m 24s in the United States. The standard version available today is just 92m 42s, although some prints are in circulation in the United States - where the film is in the Public Domain - that retain the additional scenes that constitute the original American release.
Wells originally wanted the music to be recorded in advance, and have the film constructed around the music, but this was considered too radical and so the score, by Arthur Bliss, was fitted to the film afterwards in a more conventional way. A concert suite drawn from the film has remained popular; as of 2003, there are about half-a-dozen recordings of it in print.
After filming had already begun, the Hungarian abstract artist László Moholy-Nagy was commissioned to produce some of the effects sequences for re-building of Everytown. Moholy-Nagy's approach was partly to treat it as an abstract light show but only some 90 seconds of material was used (e.g. a protective-suited figure behind corrugated glass), although in the autumn of 1975 a researcher found a further four discarded sequences.
The use of gas bombs is very much part of the film, from the poison gas used early in the war to the sleeping gas used by the airmen of Wings Over the World. In real life, in the build-up to the Second World War, there was much concern that the Germans would use poison gas, which they had done during the Great War. Civilians were required to carry gas masks and were trained in their use. When war did break out, however, the Germans did not use gas for military purposes.
The single world government having engineers, scientist and inventors as the rulers mimics the ideology of the concept of Technocracy where those of the greatest skill and intellect in various vocations would be the leaders.
In the United States, although the 92m 42s version is most prevalent, a version is also in circulation that includes the four pieces of footage that were in the 96m 24s print, but not the 92m 42s version, although due to cuts elsewhere it actually runs shorter than the latter. A cut version of the 92m 42s print was digitally restored and film colorization by Legend Films and released on DVD in the United States in 2007.
In May 2007, Network DVD in the UK released a digitally-restored copy of the 96m 24s version, which to date is the longest version available on DVD anywhere in the world. The two-disc set also contains a "Virtual Extended Version" with most of the missing and/or unfilmed parts of the film represented with production photographs and script extracts.