Sky Liner

In New York, State Department official George Eakins receives sealed orders from Washington as he is about to leave for a conference in Los Angeles. Soon after, Amy Winthrop, Eakins' secretary, leaves the office and phones someone to inform them about the letter's arrival. A shadowy figure then enters Eakins' office and pistol whips him. At La Guardia airport, a Mr. Smith, posing as Eakins, purchases a ticket for a friend, who is to join the flight to Washington in Chicago. Meanwhile, in Chicago, Smith's friend, Bokejian, is negotiating the sale of his country's oil and mineral rights for a large sum of cash. As the passengers board the plane in New York, Smith seeks out Amy and informs her that he is taking Eakins' place, as he hit him too hard and he died. Also on board the plane are a film actress, two spinsters, an eloping couple, an obnoxious child singer and her mother, and two murderous crooks, J. S. Conningsby and Ben Howard. The pilot, Captain Fairchild, informs Carol, the senior stewardess, that just before take-off he received a message that an FBI agent is on board and that they are to cooperate with him should the need arise. After Carol confuses Smith for the FBI man, passenger Steve Blair introduces himself to her as an accountant. When the plane lands in Chicago, Bokejian boards and is surprised to see Sir Harry Finneston, who recognizes him from his days in the British colonial service and congratulates him on his rise to power in his country's government. Back in the air, some of the passengers learn about the presence of an FBI man on board and speculate about whom he is following. After Steve shows Carol his card identifying him as a special investigator for the government, Smith and Bokejian meet in the washroom, where Smith tells Bokejian that he wants more money for the envelope that he has taken from Eakins. Later, when he opens the envelope, Bokejian discovers only blank sheets of State Department notepaper and becomes enraged. When Smith is later found dead in the washroom, the pilot informs Amy, and Steve takes charge of the investigation. Captain Fairchild then decides that they will have to land at the nearest airport, where they will be met by a doctor and police officials. However, there is heavy fog all the way to the coast, but Steve, who tells Fairchild that he suspects murder and has been following Amy, insists that the plane land at an Army air base, Jackson Field. Steve talks on the radio with Colonel Hanson at the base and tells him that it is essential to national security that he have an autopsy done on Smith before the flight reaches Los Angeles. Carol announces to the passengers that someone has taken ill and they have to make an emergency landing. On the ground, a doctor informs Steve that he cannot determine the cause of Smith's death and will need to perform a thorough autopsy, which could take over an hour. Steve decides to allow the flight to continue and asks the doctor to radio the results of the autopsy to him. He also tells Fairchild that Amy is suspected of being involved in espionage activities, and the description he was given of Eakins does not match the dead man. After Steve asks Hanson to wire New York to find out if Eakins left there, the flight resumes and Steve receives a message from the doctor stating that the deceased was killed by an injection of curare in a solution of fountain pen ink. Steve also learns that Eakins has been found dead in his office. Steve radios his field office in Los Angeles to meet the flight at the Burbank airport, then, identifying himself as an FBI agent, announces to the passengers that a passenger has been murdered, and that they will all be held for questioning when the plane lands. Finneston and Bokejian tell Steve that they should have diplomatic immunity, but he rebuffs them. When Steve interrogates Amy, trying to discover her motivation for treason, she reveals that Smith was her husband and was involved in a deal with Bokejian. Later, after Conningsby draws a gun on Steve and forces him to arrange for the plane to land at Los Angeles Muncipal Airport instead of Burbank, he knocks Steve out. However, the plane is met by FBI men who have been covering both airports. Conningsby attempts to escape but Steve recovers and helps his fellow agents in a gun battle. When Steve asks to see Bokejian's fountain pen, he attempts to stab Steve with it and they grapple for possession until Steve is victorious. Steve then explains to Carol that the State Department was concerned about information being leaked and gave Eakins blank orders. Smith killed Eakins to get the orders to sell to Bokejian, but believing that he was double-crossed, Bokejian killed Smith. Their job completed, Steve and Carol go off to have coffee together.