American industrialist Jonas Bracken (Robert Culp) learns that his wife Ellen (Susannah York) and his kids Jimmy (Simon Harrison) and Susie (Stephany Mathews) have been kidnapped from their home in Greece by the World Activist Revolutionary Army, a terrorist organization dedicated to spreading chaos, who demand a ransom of $5 million, then a large amount of arms and ammunition. Greek police investigate, led by Inspector Nikolidis (Charles Aznavour), who is more concerned with capturing the terrorists than with keeping the Brackens safe. Ellen's ex-husband Jim McCabe (James Coburn) has his own plan - he hires the members of a hang glider flying circus to rescue the prisoners from the isolated mountain monastery where they are being kept.
Sky Riders contains examples of:
- Buzzing the Deck: Terrorists swoop down on Jim in a helicopter in order to knock him off a cliff. Instead, Jim grabs on to one of the skids.
- Cut-and-Paste Note: Any communication from the terrorists that isn't over the radio is in the form of these letters.
- The Door Slams You: One of the hang gliders flings a door open, knocking over one of the terrorists.
- Food Slap: Ellen demands that a guard give her and her children blankets and feed them something other than gray glop, saying her children have become sick. The guard replies that this is a people's prison and the prisoners live in the same conditions as everyone else. Ellen throws some of the glop at the guard through the bars. The guard beats her until another terrorist intervenes.
- Girlish Pigtails: Three-year-old Susie wears her blonde hair in pigtails.
- Hollywood Darkness: The hang gliders approach the monastery under cover of a day for night shot, complete with shadows, light shining off rocks, and puffy clouds in the slightly darkened sky.
- Outside Ride: While dangling from the terrorists' helicopter's skid, Jim shoots the copter, forcing it to land.
- Phone-Trace Race: Attempted. While talking on the radio with the terrorists, Bracken tries to keep them talking while the police triangulate their location. But the location turns out to be a decoy. Police officers surround a truck they find there, and when one of them opens the doors, it turns out to be a Booby Trap that detonates several sticks of dynamite and kills six officers.
- Pistol-Whipping: One of the terrorists used to believe that peaceful protest was the way to go. One day a cop smashed the butt of a rifle into his face with little provocation, leaving him with a scar. That was when he realized that there can be no dialogue between the haves and the have nots, and so he became a terrorist.
- Special Thanks: "The producers express gratitude to the various government ministries and the armed forces of Greece without whose assistance this film could not have been made."