Murder in the Air (1997)

The airplane Mark and Amanda are taking for a medical conference in Zurich (Switzerland) is delayed to wait for alternative co-pilot Ron Manners, a reputed womanizer. Mark observes the staff have their own problems on top of work, a troublemaker, a female jeweler who ignores the smoking ban. Then Mark finds Ron's corpse in the toilet, neck broken, and starts looking for the murderer among over 100 passengers plus staff after contacting Steve, airplanes being extraterritorial. Then several crew members are found unconscious, cause unknown, leaving no pilot, just passenger Martin Donner Kingston, who has US Air Force experience. Steve finds the originally scheduled co-pilot, knocked down but alive; while Jesse treats his seizure Mark figures out it's a binary poison triggered by aspirin, possibly administered at the hotel all staff except local Deb slept in, the lab confirms: it's a spy toxin. Steve has terrible news after checking the passengers' records...