Aspiring comic book artistJosh Baker meets a young woman named Cheryl on the streets of New York City, who proceeds to collapse and is rushed to a hospital by an ambulance. When Josh arrives at the hospital, he is shocked to find that there is no record of Cheryl ever being admitted and he soon learns another startling discovery, Cheryl's roommate also vanished after being picked up by the same ambulance. Convinced that there is some sort of conspiracy going on, Josh proceeds to investigate the disappearances, despite the overt disdain and discouragement from Lt. Spencer.
Cohen later said he was inspired by "the concept of taking something that is thought of as being benign or benevolent... or anything else that has a safe and wholesome image, and turning it into an object of terror." He had done this for It's Alive and The Stuff and wanted to do it with ambulances. "When you hear or see an ambulance on the street, it’s usually considered to be something that is going to rescue you and take care of you, a vehicle of mercy," said Cohen. "In this story, it’s actually a vehicle of murder. The whole idea of an ambulance that suddenly arrives from nowhere, picks people up, and takes them away to some dark place where they are never seen or heard of again was completely original and creepy." Cohen says at one stage the financiers wanted a "classier" title than The Ambulance so he retitled it In Thin Air. They changed their mind and the film went back to being called The Ambulance. In the May, 1990 edition of his column Stan's Soapbox, Stan Lee mentions playing himself in a scene in "an adventure mystery called 'Into Thin Air'" and refers to the name change in a later column. Cohen wanted to cast John Travolta or Jim Carrey in the lead but his producers refused. Donald Trump made a small cameo in a deleted scene. Jamie Lee Curtis was originally considered to play Officer Sandra Malloy The role of the villain was originally played by Wesley Addy. However Cohen was unhappy with his performance and recast the role with Eric Braeden. Braeden's casting came at the suggestion of Cohen's mother who was a fan of The Young and the Restless.
