The amount of hash strapped to Billy Hayes' body differs from when he was first frisked in the airport and later when he was in the police interrogation room.
When Billy Hayes, Max, and Jimmy are trying to escape through the catacomb tunnels, a fourth unnamed prisoner joins them. However, when they realize that it is a dead end, the fourth person is not seen again.
It is true that Billy Hayes was beaten with a stick by a guard for stealing a blanket because he was cold in his jail cell the first night. He was hit with a stick, but he was not hung up and beaten on a torture rack as shown.
Billy Hayes never had any real issues with the Turkish people and made some friends in prison. He did not have any profanity rant when the Istanbul Appellate Court forced the trail judge to give him a minimum sentence of thirty years, but he actually begged for forgiveness when he spoke before receiving his new sentence.
Several of the month and date cards shown in the movie are inaccurate, especially in the last third of the film. The movie displays Billy Hayes' decent into an almost complete vegetable-state based on how the Turks treated him. In Hayes' Midnight Express book, he does not suffer the mental hardship and physical abuse as shown in the movie. In contrast, the book talks more about the filthy conditions at the prison, not about Hayes' decaying health or any issues with the Turkish people.
Muslim prayer is depicted incorrectly. Muslim prayer has definite steps and rules, and there's always a leader to the prayer when more than two are praying.
Some sources claim that Billy Hayes gives the unnamed man, whom he meets when strip-searched, the name of "Tex". However, at no point in the film does Hayes call him this. He is only named "Tex", because he speaks to Hayes with a Southern accent.
The Turkish spoken by the Turkish characters in the film is uniformly broken. The actors are obviously not Turkish; sometimes the language is so broken it is difficult for native speakers to understand what they are saying.
The movie is set in 1970. When Billy Hayes makes a visit to the toilet at the airport to wash his face, there is a poster on the wall showing a shot of the Bosphorus Bridge, which was built in 1973.
The fez worn by several Turkish men in the movie has been extremely rare in Turkey since 1925, when it was abolished by Mustafa Kemal Atatürk (the leader and founder of the Republic of Turkey) in an attempt to "westernize" the country.
In the bus that takes Billy Hayes and Susan to the plane, Susan is reading a newspaper and says, "Janis Joplin died yesterday." Hayes was arrested at Istanbul Airport on October 6, 1970; Joplin died on October 4, 1970.
When Susan goes to visit Bill, a crew member can be seen reflected in the glass.