The outdoor set used for the 747 crash site was so convincing that pilots landing at Toronto Airport were radioing in what they thought was a recent airplane crash.
To create the time-travel effects of the Gate, cinematographer Rene Ohashi produced the ghostly shimmering lights by spinning metal wheels covered in Mylar.
John Varley originally wrote the short story "Air Raid" in 1977. At the time, it was optioned as a project for FX director Douglas Trumbull, director of Silent Running and Brainstorm. The plan was to make it a vehicle for Paul Newman and Jane Fonda. Trumbull's production fell through, only for it to be inherited first by Randal Kleiser and then Richard Rush. With all the comings and goings over the years, Varley was able to first turn it into a novel in 1983 and then a screenplay.
According to John Varley's original manuscript, Smith's role in history was critical to the National Transportation Safety Board (NTSB), and eventually became the director. He died in old age by falling off his houseboat and drowning.
The trivia items below may give away important plot points.
The film has a second ending, which was only released to international audiences. In that version, Louise and Bill materialize in a Garden of Eden in the far future, and fall into each other's arms.