During a routine flight to Minneapolis, a passenger (Susan Dey) aboard Global Airways Flight 502, a Boeing 707, discovers a bomb threat written in lipstick on the mirror of a first-class bathroom. Captain Hank O'Hara (Charlton Heston) believes it to be a hoax, but when a second handwritten threat is left on a stewardess's serving tray he is convinced to take the cryptic threats seriously and follows the instructions -- "Bomb on plane divert to Anchorage Alaska. No Joke, No Tricks. Death"—by changing course for Alaska. To avoid an explosive decompression if a bomb goes off, he flies at lower altitude, increasing fuel consumption.