During a major snow storm, Transcon Airways Flight 602, Boeing 727 airliner piloted by Captain Pete Douglas (David Janssen), First Officer Stan Burkhart (Christopher George) and Second Officer Mike Fuller (Don Meredith) on a flight from Los Angeles to New York, makes a scheduled stop in Salt Lake City. Greco (Marjoe Gortner), a two-time killer in the custody of Sam Riese, a Federal Marshal (Broderick Crawford) comes aboard. Among the passengers are Burkhart's girlfriend, nurse Susan McKenzie (Margaret Blye) and Joseph Mannheim (Ray Milland) a disillusioned and possibly disgraced medical doctor drowning his problems with scotch. Captain Douglas has a family emergency that is making him anxious to return home as soon as possible.
After leaving Salt Lake City, the Federal Marshal suffers a fatal heart attack and his prisoner gets his gun. In the ensuing scuffle, Greco fires wildly, wounding the pilot and Susan McKenzie, as well as puncturing the hydraulic oil lines controlling all major systems on the airliner, including flaps and landing gear. Fuller tackles Greco and knocks him unconscious, disarming him and putting one of the passengers, an Army officer, in charge of the prisoner. While the remaining flight crew take charge of the cockpit, head flight attendant Terry Dunlap (Shani Wallis) with flight attendants Cathy Armello (Lynda Day George) and Cindy Jensen (Christopher Norris), tend to the passengers.
A severe snowstorm has closed nearly all Midwestern airports, thus forcing the crippled aircraft with its badly wounded passengers to endure a three-hour flight to Chicago. The extended flight time puts the survival of the wounded pilot and passenger tended by Dr. Mannheim, in a precarious state and it is questionable whether the co-pilot and flight engineer will have sufficient control to land the aircraft safely. A crosswind makes the landing at Chicago extremely tricky and Burkhart and Fuller must wrestle with the controls to keep the 727 from veering off the runway. The pilots see the emergency vehicles off to the aircraft's right as they touch down on the runway with several hard bounces. As the 727 slows down, the pilots must continue their fight to keep the aircraft under control.
As the emergency vehicles approach the aircraft, Greco makes another escape attempt but is foiled by Burkhart who subdues him. Captain Douglas and Susan McKenzie are placed aboard ambulances and rushed to a Chicago hospital where Douglas finds out that his wife Kitty (Jane Powell) has been undergoing a breast cancer biopsy that has revealed a benign tumor. Dr. Manheim announces that Susan also will make a full recovery. With that news, Douglas and Burkhart are finally relieved.