Question: Steven Spielberg, is an American director, producer, and screenwriter who is considered one of the founding pioneers of the New Hollywood era, who did he co-write the unfinished film Slipstream with?

Context articles: Steven Spielberg
Influence of Stanley Kubrick
Robert Altman
Howard Hawks
Matt Charman
Steven Spielberg filmography
New Hollywood
Slipstream (unfinished film)
Easy Rider
1980s in film

Steven Allan Spielberg, {'1': ", '2': ", '3': 'KBE', '4': "} , {'1': ", '2': ", '3': 'OMRI', '4': "} (born December 18, 1946) is an American director, producer, and screenwriter.
 He is considered one of the founding pioneers of the New Hollywood era, as well as being viewed as one of the most popular directors and producers in film history.
 He is also one of the co-founders of DreamWorks Studios.
Stanley Kubrick is regarded by film critics and historians as one of the most influential directors of all time.
 Leading directors, including Martin Scorsese, Steven Spielberg, George Lucas, James Cameron, Woody Allen, Terry Gilliam, the Coen Brothers, Ridley Scott, Paul Thomas Anderson, Christopher Nolan, David Lynch, and George A. Romero, have cited Kubrick as a source of inspiration, and in the case of Spielberg, collaboration.
 In an interview for the "Eyes Wide Shut" DVD release, Steven Spielberg comments that "nobody could shoot a picture better in history", and that Kubrick told stories in a way "antithetical to the way we are accustomed to receiving stories".
 Writing in the introduction to a recent edition of Michel Ciment's "Kubrick", film director Martin Scorsese notes most of Kubrick's films were misunderstood and under-appreciated when first released, only to be considered masterpieces later on.
Robert Bernard Altman ( ; February 20, 1925 – November 20, 2006) was an American film director, screenwriter, and film producer.
 A five-time nominee of the Academy Award for Best Director and an enduring figure from the New Hollywood era, Altman was considered a "maverick" in making films with a highly naturalistic but stylized and satirical aesthetic, unlike most Hollywood films.
 He is consistently ranked as one of the greatest and most influential filmmakers in American cinema.
Howard Winchester Hawks (May 30, 1896December 26, 1977) was an American film director, producer and screenwriter of the classic Hollywood era.
 Critic Leonard Maltin called him "the greatest American director who is not a household name."
Matt Charman is a British screenwriter, playwright, and producer.
 He was nominated for an Academy Award for best original screenplay for his 2015 film "Bridge of Spies", directed by Steven Spielberg and co-written with Joel and Ethan Coen.
 Charman started out writing for theatre, making his breakthrough as writer-in-residence at London’s National Theatre, where then director Nicholas Hytner described Charman as having "a priceless nose for a story."
 He recently wrote the pilot episode of "Oasis", a sci-fi drama for Amazon Video adapting Michel Faber's "The Book of Strange New Things", and is working on a second movie for Steven Spielberg's Amblin Partners, based on Walter Cronkite’s 1968 visit to Vietnam.
Steven Spielberg (born December 18, 1946) is an American director, producer, and screenwriter.
 He is considered one of the founding pioneers of the New Hollywood era, as well as being viewed as one of the most popular directors and producers in film history.
 He is also one of the co-founders of DreamWorks Studios.
New Hollywood, sometimes referred to as the "American New Wave", usually refers to a movement in American film history from the mid-to-late 1960s ("Bonnie and Clyde", "The Graduate" and "Easy Rider") to the early 1980s ("Heaven's Gate", "One from the Heart") when a new generation of young filmmakers came to prominence in United States, influencing the types of films produced, their production and marketing, and the way major studios approached film-making.
 In New Hollywood films, the film director, rather than the studio, took on a key authorial role.
 The definition of New Hollywood varies, depending on the author, with some of them defining it as a movement and others as a period.
 The span of the period is also a subject of debate, as well as its integrity, as some authors, such as Thomas Schatz, argue that the New Hollywood consist of several different movements.
 The films made in this movement are stylistically characterized in that their narrative often strongly deviated from classical norms.
Slipstream is a film about bicycle racers directed and written by Steven Spielberg and Roger Ernest that went unfinished.
 Ernest later appeared in Spielberg's "The Sugarland Express" and "Close Encounters of the Third Kind".
 "Slipstream" also co-starred Tony Bill, who was already an established actor, and Jim Baxes, who went on to co-star in 1975 in the TV show "SWAT" under the stage name James Coleman.
Easy Rider is a 1969 American independent road drama film written by Peter Fonda, Dennis Hopper, and Terry Southern, produced by Fonda, and directed by Hopper.
 Fonda and Hopper played two bikers who travel through the American Southwest and South carrying the proceeds from a drug deal.
 The success of "Easy Rider" helped spark the New Hollywood era of filmmaking during the early 1970s.
The decade of the 1980s in Western Cinema saw the return of studio-driven pictures, coming from the filmmaker-driven New Hollywood era of the 1970s.
 The period was when "high concept" films gained popularity, where movies were to be easily marketable and understandable, and, therefore, they had short cinematic plots that could be summarized in one or two sentences.
 The modern Hollywood blockbuster is the most popular film format from the 1980s.
 Producer Don Simpson is usually credited with the creation of the high-concept picture of the modern Hollywood blockbuster.