A mad bomber forces a jet to re-route to Moscow.

At Oakland International Airport, Global Airlines captain Henry O'Hara, his crew and flight attendants prepare for flight 502 to Minneapolis. After Hank, co-pilot Sam Allen and navigator John Bimonte complete their flight check, Hank is summoned to the gate, where a young soldier, Sgt. Jerome K. Weber, is demanding a seat, despite being wait-listed. Weber explains that he is on a twenty-four hour pass and must be in Minneapolis for his sister's wedding. First class passenger and jazz musician Gary Brown, who is checking in, offers to give up the seat he normally purchases for his cello to Weber, provided Hank can assure him that his instrument will travel safely. Hank approves placing Weber in first class, then escorts Gary and his cello to the plane. As flight 502 nears departure, head flight attendant Angela Thacher welcomes aboard first class passengers including young Elly Brewster, Senator Arne Lindner and his college-aged son Peter and eight-months pregnant Harriet Stevens. Shortly after takeoff, flight 502 receives a message for Lindner from the White House requesting his immediate return to Washington, D.C. After the flight reaches its cruising altitude and the passengers can move through the cabin, Elly chats briefly with Peter on her way to the lavatory. Moments later, Elly rushes out of the toilet to report to Angela that there is something wrong inside. After verifying Elly's claim, Angela summons Hank, who finds a message scrawled on the lavatory mirror stating that there is a bomb on board and demanding that the plane be diverted to Anchorage, Alaska. Hank searches the small room and finds a cylindrical object in the waste bin. After questioning Elly to ensure that she did not write the message, Hank returns to the cockpit, where he informs Sam and John of the message and shows them the cylindrical object, which he presumes is a defunct detonator meant to underscore the seriousness of the threat. When Sam observes that Global's earlier direct flight from Oakland to Anchorage was canceled that morning, Hank asks John to plot a course to Anchorage, then radios the nearest air control. Flight controller Walter Brandt, a former military acquaintance of Hank's, receives his message and immediately informs the FBI. Later, Angela and fellow flight attendant Lovejoy Wells report that only those in first class have access to the lavatory containing the message. Lovejoy adds that both Weber and Gary are drinking heavily and suggests that the cello case might hold the bomb. Recalling that Lindner and Peter were to make a fishing trip, Hank orders their carry-on sporting equipment examined, then summons Lindner to the cockpit. Although displeased at being a suspect, Lindner points out that he is not important enough to prompt a hijacking, despite a Presidential summons. While departing the flight deck, Lindner stumbles over Angela's meal cart where moments later she finds a note written in lipstick that states: "Change course for Anchorage now or die." Growing increasingly nervous after giving the note to Hank, Angela reflects on her recent broken romance with Hank, whom she still loves despite his return to his wife and family, and her own current involvement with Sam. Upon confirmation of the new course to Anchorage, Hank also receives information that the weather is stormy, with zero visibility, and requests a military representative to talk him down. Meanwhile, in first class, Weber grows steadily drunker and takes pills that he confesses to Gary are "uppers." Weber then realizes they are changing course, and moments later, Hank informs the passengers of the threat and their new destination. A little later, wary of Weber's increasingly erratic behavior, Gary approaches Angela in the galley and asks to see Hank to whom he confides his suspicion that Weber is the hijacker. Hank passes on the information to the FBI. As night falls, Anchorage air control puts Sgt. Ben Puzo on the radio with Hank to guide his blind landing during the storm. Refusing to take a practice run because of the jet's lack of fuel, Hank insists on a direct approach. Some miles from the airport, however, Puzo notes a small craft on the radar that fails to respond to radio calls and is directly in the jet's flight path. Deducing that the smaller plane has an emergency, Puzo orders Hank to circle around, but despite the zero visibility, Hank opts to bank the jet sharply up and over, which takes them out of the smaller plane's course. After Puzo confirms the jet is in front of the smaller plane, he guides Hank to a safe landing into the storm-lashed Anchorage airport. Once the jet stops on the runway, an FBI agent contacts Hank to inform him that Weber is actually Jerome K. Weller, who is facing a military psychiatric discharge. Hank requests that the agent restrain his men until the passengers have been evacuated safely while Weber peers out the window and fantasizes about a hero's welcome by American military leaders. When he instead sees armed FBI agents nearby, he panics and engages in a scuffle with Angela and several first class passengers as he tries to grab his bag. Weber holds off the others by brandishing a gun and grenade, then forces Angela to escort him to the flight deck. While Hank diverts Weber with several questions, Angela returns to the passenger cabin and oversees their hasty evacuation down the emergency slide at the back of the plane. After demanding that Hank fly him to Moscow, Weber realizes the passengers are escaping and intervenes before those in first class can flee. Lovejoy reveals that the stress of the past several hours has forced Harriet to go into labor, but Weber refuses to let her deplane. Angered to see a van of photographers drive by the plane, Weber shoots one of them, then orders the plane refueled and prepared for takeoff with the remaining passengers as hostages. As the plane heads toward Moscow, American air control tries in vain to contact the Soviet Union to explain the situation. Meanwhile, Angela and the others help Harriet deliver her baby. Upon reaching Soviet airspace, the Global flight is immediately surrounded by a quartet of military fighter jets which then escort the craft to within miles of Moscow's public airport. On landing, Weber presents himself on the radio as a military defector and allows all the passengers except Hank to deplane. Weber then reveals that he never had a bomb, only grenades and guns. Again envisioning a hero's welcome, Weber dresses carefully, only to realize with distress that the plane is surrounded by armed Soviet soldiers. When Weber hysterically dons a harness loaded with grenades, Hank attacks him, but is wounded. Pushing the injured pilot down the ramp in front of him as a shield, Weber deplanes, but when Hank leaps away, the soldiers fire on Weber who then falls upon a live grenade and is blown up.