Slipstream is set in a dystopian future, following a global environmental disaster. A voice over at the beginning of the film explains that a doomsday event, called the "Convergence", has destroyed the balance of the world's weather systems, with the result that the jet stream has expanded to the planet's surface, with the surface scoured by winds far surpassing anything ever seen before, destroying cities and entire nations. Many bizarre communities have survived in the valleys and caves, some regressing to primitive states, others embracing advanced technologies. Many are isolationist and some are attacked by marauding bandits. Ground transport is no longer possible due to the atmospheric conditions, but skilled pilots can travel by air, following the fierce winds and travelling with their flow, a practice known as "riding the slipstream". The remnants of society have therefore become airborne; most now reside on high precipices or in caves beneath the howling Slipstream. It is also stated that nobody has ever been to the ends of the Slipstream, because atmospheric conditions there make human survival impossible.
The film opens with an unnamed man (Peck), running down a canyon, being harassed by an aeroplane, which drives him onto a precipice. The plane lands and its occupants, two bounty hunters, Will Tasker (Hamill) and Belitski (Kitty Aldridge), chase the man and shoot him through the arm with a grappling hook. The fugitive looks at his arm, but seems intrigued rather than distressed. Tasker pulls on the rope, and the man tumbles down the side of the canyon, but once again is not harmed. Immediately after his fall, the fugitive recites the words of famous World War II aviator and poet John Gillespie Magee, Jr., "I have slipped the surly bonds of Earth - put out my hand and touched the Face of God.", from the poem High Flight.
The bounty hunters take the man prisoner and fly to a busy civilian airstrip, where he stands beside them, handcuffed, as they eat in the airstrip's diner. There they encounter Matt Owens (Paxton), a hustler and smalltime arms dealer. He makes a pass at Belitski and she nearly breaks his arm, and he then tries to sell contraband grenades to Tasker. It is then revealed that Tasker and Belitski are part of the remnants of a law enforcement agency, trying to keep the peace in what is left of society. Byron is wanted for murder, and they are bringing him to justice. Tasker seizes Owens' weapons, but as the pair are leaving, Owens kidnaps Byron so that he can claim the large reward for himself, and they flee, but not before Belitski shoots Owens with a dart, both poisoning him and planting a tracking device in his body, enabling Belitski and Tasker to follow the fugitives.
Owens and Byron first fly to Owen's home, Hell's Kitchen, where Byron heals a boy blinded by cataracts, and Owens begins to wonder if Byron is more than he appears. After getting lost, they land at the home of a cult of cave-dwellers who worship the Slipstream and who have recently been under attack by bandits. Byron attempts to help, lifting a heavy milling stone off the cult's leader, Avatar. Avatar, in his dying breaths, curses Byron as being part of the out-of-control technological advancements that lead to Convergence. The cultists decide to let the wind decide what to do with him, and tie him to a massive kite. The bounty hunters arrive in the middle of a windstorm, and Owens bargains with them to work together to get Byron down. Tasker reveals to Owens that Byron is an android. After a rough landing from the destroyed kite, Belitski allows Byron and Owens to get away, diving back into the deadly windstorm to search for her partner. Another visitor to the valley, Ariel, helps Byron and Owens escape the scouring winds, and convinces them to give her a lift home. Ariel takes them to her people, a group of hedonists, who inhabit a fortified underground museum. Byron's knowledge and appreciation of the museum's ancient contents lead to Ariel becoming emotionally attached to him. Byron and Ariel spend the night together in an African Savannah exhibit, while Owens gets drunk and hooks up with a local girl. The local girl helps Owen decide to free Byron, who has become his friend. Later, Byron explains more of his past, revealing that the man he killed was his master. Byron also excitedly tells Matt that he has slept for the first time, and that he dreamed of a land at the end of the Slipstream, inhabited by other androids.
Soon after, having tracked the trio to the museum, Tasker and Belitski force entry, killing the guards and some of its inhabitants. After beating the Curator (F. Murray Abraham), Tasker forces the rest to find the fugitives. Byron is captured, and Owens is knocked down. Belitski confronts Owens and shoots him in the chest with a dart; Owens retaliates by knocking her out, and handcuffing her to a bed. She wakes and tells him that the dart is the antidote to the poison. He sets off after Tasker. A shootout ensues in which Tasker kills Ariel. Enraged, Byron pursues Tasker to his plane. Tasker shoots Byron, to no effect, so he then tries to run Byron down as he takes off, but Byron manages to jump on, and smash his way into the cockpit. The pair struggle, but as Byron is on the verge of killing him, Tasker quotes the Magee poem and Byron relents. He then attempts to regain control of the damaged aircraft by using the control wires, but he is unsuccessful, and it crashes. Tasker is killed, but Byron, being an android, survives. He returns to the museum to find that Belitski and Owens are now a couple. The film ends with Byron leaving to seek his 'promised land'.Mark Hamill as Will Tasker, a self-proclaimed lawman, although his profession seems to be more akin to that of a bounty hunter.
Kitty Aldridge as Belitski, Tasker's female companion.
Bill Paxton as Matt Owens, a smuggler and small-time arms dealer.
Bob Peck as Byron, an android with superhuman powers.
Eleanor David as Ariel, a member of a hedonistic cult who live in an underground museum.
Robbie Coltrane as Montclaire, an associate of Owens in the mountain caves.
Ben Kingsley as Avatar, the elderly leader of the wind-worshipping cult who see the slipstream as the manifestation of God.
F. Murray Abraham as Cornelius, the curator of a vast underground museum.
Slipstream was the second feature Gary Kurtz made as a producer after splitting from his former creative partner George Lucas. Kurtz's early production credits included the films Chandler and Monte Hellman's cult road movie Two Lane Blacktop (1971). He then began his hugely successful collaboration with George Lucas by producing Lucas' commercial breakthrough, the low-budget American Graffiti (1973), which went on to become one of the most profitable films of all time. Kurtz then produced, worked as a second-unit director, and played a major creative role in the first two Star Wars films, but the partnership ended acrimoniously in the interval between Empire and the third instalment of the series, Return of the Jedi, when Lucas and Kurtz fell out over the creative and commercial direction of the franchise.
Following the acrimonious split with Lucas, Kurtz acted as executive producer on the fantasy film Return to Oz, which was not a commercial success. He returned to commercial favour as the producer of the hit fantasy film The Dark Crystal in 1982. He evidently hoped that he could recapture his earlier success in science fiction with Slipstream, which co-starred popular actors from two of the major sci-fi franchises of the period - Hamill from Star Wars, and Paxton from Aliens. However, in spite of the many prominent names involved, including Kurtz, the cast, and distinguished Hollywood composer Elmer Bernstein, Slipstream proved to be a disastrous financial and critical flop. Its failure reportedly drove Kurtz into bankruptcy, and as a result, the film is now in the public domain.
Slipstream was filmed in Cappadocia, Turkey, Ireland, and Pinewood Studios, Iver Heath, Buckinghamshire, England, UK.
Slipstream had a short cinema run in the United Kingdom, where it was considered a flop, and Australia, where the film grossed just $66,836 during its entire theatrical run. The film was never released in theaters in North America and enjoyed only moderate VHS sales. The film was released on videocassette by M.C.E.G. Virgin Home Entertainment in 1990. Several budget DVD copies of Slipstream have been released. Fans awaiting a director's cut have been disappointed after producer Gary Kurtz said in an interview that the script was originally much more violent, but that these violent scenes, which would have made the plot more coherent, were never filmed.
It has also been released as a DVD double feature by "Destra Entertainment - Payless", the other feature being 1967's In the Year 2889.
As of August 2017, the film has a "rotten" score on Rotten Tomatoes of 20%.