Plot summary

Mr. Dennis Scott (Jack Hawkins) shows up for his first day of work as Chief of Metallurgy at the Royal Aircraft Establishment, Farnborough, England, UK, and reports to Sir John (Ronald Squire), the Director. Sir John immediately hands Scott over to Major Pearl (Maurice Denham), aka "The Pearl of Great Price," for a tour of the testing facilities. The various tests that the RAE scientists have set up fascinate Scott, especially the last one, a prolonged "vibration test" of the double-elevator tail group of the RAE's latest creation, the Reindeer airliner, of which several hundred were delivered recently to the Trans-Atlantic Aircraft Corporation. Major Pearl cannot make himself heard over the tremendous noise, so he shuts down the test, thus provoking the lone scientist, Theodore Honey (James Stewart), to protest that the test must continue. Honey is very brusque and not very sociable at all, but Pearl explains to Scott that the RAE has had him since his days as a Rhodes Scholar from the USA and consider him quite valuable.Scott asks Honey the point of his exercise, and Honey says simply, "I expect the tail to fall off." Scott is not satisfied with that and offers to give Honey a lift to his home so that he can have an opportunity to press Honey further. Honey's theory is that the repeated vibration of thousands of flying hours must produce energy, and since that energy is not released as heat or in any other form, the metal itself must absorb it and eventually fail, at 1440 flying hours. Honey is quite oblivious to the consideration that people's lives might ride on his theory and calculations, and protests that as a scientist he cannot afford to concern himself with people.Honey's thoroughly eccentric attitudes carry forward into his home life. His wife is dead, but his daughter Elspeth (Janette Scott) remains, and he has been home-schooling her with a regimen of near-constant study. Scott finds Elspeth pleasant enough, but worries that she is even less socially adept even than Honey, difficult as Scott finds that to imagine.The next morning, Scott hoists a pint with an old friend of his, a test pilot named Bill Penworthy (David Hutcheson). The two men talk of a mutual friend, Harry Ward, a pilot for TAAC, who died in a crash in Labrador under mysterious circumstances. Penworthy voices contempt for a system that blithely attributes a mysterious airline crash to "pilot's error" just because the pilot is dead and thus unable to defend his reputation. The circumstances of the crash were these: the aircraft abruptly lost altitude, as if the pilot had taken a crash dive, something that Ward would never have done. But what makes Scott take Penworthy's story even more seriously is the make of the aircraft: a Reindeer.Scott asks Sir John's secretary, a man named Johnson (Hugh Cross), to show him every available photograph of the wreckage of Waring's plane. Johnson alarms him with two revelations: the aircraft had 1407 hours on it when it went down, and the tail group was never found. That, of course, was the very thing that Honey was testing. Could the tail have broken off from metal fatigue, as Honey had predicted and was even now testing out?Scott brings his suspicions to Sir John, who agrees to place Honey's vibration test on a round-the-clock schedule (instead of 8 hours a day) and to send Honey to Laborador on the next available flight to find the tail group and inspect it personally. And that is how Honey finds himself boarding TAAC Flight 26 to Montreal by way of Gander, Newfoundland. But what he does not realize until he is in the air is that his aircraft is a Reindeer.Aboard the flight, Stewardess Marjorie Corder (Glynnis Johns) at first notices a very nervous man who obviously has never been in an airliner before. Then Copilot Sam Dobson (Kenneth More) dumbfounds her with the announcement that they have an aeronautical scientist on board, and points him out as that very passenger (who is, of course, Honey). Marjorie rushes to apologize to Honey, who says that this is indeed his first-ever airline fight. Then she informs him that Captain Samuelson (Niall MacGinnis) has offered to give him a VIP tour of the cockpit, and in the process informs him that he is aboard a Reindeer. That is the first thing that really worries Honey. Then, when he takes the cockpit tour, he receives news that shocks him to the core: that the aircraft already has 1422 flying hours on it, more than the aircraft that crashed in Labrador! Now he tries to press Samuelson to turn back, because if he does not, the tail will break off and everyone on board will die. Samuelson is skeptical, of course, but agrees to radio London for instructions, and to feather his inboard engines to reduce the vibratory load.Back in the passenger cabin, Honey takes time to inspect the men's lavatory, which shares a bulkhead with the galley, a bulkhead bolted to the floor. Thus determining that that is the safest place in the aircraft in the event of a crash, he breathlessly introduces himself to a prominent female passenger, a movie star named Monica Teasdale (Marlene Dietrich). At the first sight of this strange little man with his whacked out theory, she presses the call button at her seat, and Marjorie shows up to usher Honey back to his seat. He cooperates, but not before he repeats to her exactly what he tried to tell Monica about the best place to ride out a crash. Marjorie goes to apologize to Monica, and then tries to explain what Honey was trying to tell her. Monica now becomes curious, especially when the two inboard engines shut off, indicating that the captain really did take Honey seriously. Whereupon Monica insists on sitting with Honey and getting him to explain everything to her. Subsequently, Monica and Honey sit out the rest of the flight in the galley, where they make small talk that suddenly doesn't seem so small.Samuelson receives no orders except to act at his own discretion. Because he is past the point of no return (the halfway point), he flies on, but requests clearance for an immediate, straight-in landing. He lands safely enough, and then orders a complete nose-to-tail inspection. But he next orders Marjorie to confine Honey to a private room in the Gander terminal, and not to allow him back aboard for the next leg of the flight.Honey is not convinced that the safe landing proved him wrong, and believes that the next flight that that aircraft makes will be its last. So when the captain asks everyone to come back aboard, Honey jostles his way aboard the aircraft and pushes into the cockpit, where Samuelson tells him to get off and stay off. Whereupon Honey spots the landing-gear lever and pulls it, thus retracting the landing gear while the aircraft is on the ground. That, of course, makes the aircraft unflyable.Monica, astounded, makes her way to Honey and praises him for the courage of his convictions, and announces that the experience is worth any delay he might have caused. Marjorie, for her part, is simply worried about the consequences to Honey of his actions.Sir John is furious, as much with the reaction of the press, not to mention the temperamental Sir David Moon (Hugh Wakefield), President of TAAC, as with Honey's actions, though Johnson finds the whole incident very funny. Sir John must also send an RAF pilot to fetch Honey back to Farnborough, as no TAAC pilot will dare have him as a passenger, and also send another investigator to Laborador to finish what Honey had set out to do there. In the middle of the excitement, Monica introduces herself to Sir John and tells him frankly that she was quite afraid that Honey's bosses would throw him to the wolves, a thing she did not wish to see happen.Honey returns to his laboratory and finds that others are running his experiment without him. He protests to Sir John, who informs him that he has to undergo psychological testing, while the vibration test will now run around the clock, either to failure or to 1440 hours. Honey then returns home to find that Marjorie has made it to his home ahead of him and has settled in as his housekeeper. Honey is very much worried about having done such a "crazy" thing, something that violates every rule of an ordered life that he had set for himself, but also knows that, given the same or similar circumstances, he would do the same thing again. Honey then expresses concern for the gossip that Marjorie's presence in his flat might cause, so she makes a quick trip to retrieve her nurse's uniform. (In that era, all flight attendants were recruited from among the ranks of registered nurses.)And so, when Monica comes to pay a call on Honey, she finds Marjorie there. Monica and Marjorie have a long chat, at the end of which Monica decides that she is not cut out to mix into Honey's life (a thing that no one should go into only halfway), and will return to making motion pictures to make sure that her life will have the meaning that Honey said it had.The experiment continues, but at 1440 hours the tail group does not fail. Honey returns home and confesses his failure to Marjorie, who tells him that if he really believes in his theory, he must defend it. He also has a heart-to-heart with Elspeth, who for the first time in her young life is seriously upset about her lack of any sort of socialization.Honey faces dismissal from the Establishment, and TAAC will not take its Reindeers out of service on account of Honey's theories. Whereupon Honey gives notice to the Establishment and threatens to wreck any Reindeer that is about to take off, and shouldn't, until people are simply afraid to fly on such aircraft.Honey returns to his flat and confesses that he has lost everything to Marjorie. Marjorie comforts him as best she can, and then announces that she will marry him, because he is so like a little boy who needs someone to look after him (especially after she discovers seven months' worth of payroll cheques that he has never deposited!).Back at the meeting, Sir John and Scott discuss Honey's threat, when Johnson rushes to Sir John with an urgent message: the investigator who had gone to Laborador in Honey's place has found the tail group, and that it had indeed failed from metal fatigue! Then Sir David Moon delivers his own breathless report: when the Reindeer that Honey had wrecked had undergone its repair, and taken off for a simple airworthiness test, had made a perfect landing, only to have the tail fall off as it taxied to the hangar!Scott and Sir John rush breathlessly to Honey's section of the laboratory to tell him that two reports from Gander and Labrador bear him out completely. Honey, with Marjorie by his side, acknowledges the reports but is still wondering why his own experiment failed. Sir John again tells him that the reports have vindicated him, when at that very instant the tail group breaks in half and crashes to the floor. As Sir John and Scott congratulate one another, Honey notices a swinging thermometer, and realizes at once that his experiment had not failed, but simply took longer than he calculated because he ran it in a heated shed, and that his own airliner had made it to Gander because it had piled up its flying hours serving a tropical route.