There are a few short stories by J G Ballard from the early 60s that seem to have taken their titles from lines of dialogue in this film, such as the short story collection The 4-Dimensional Nightmare.
A reviewer wrote: "For some reason the sound of jet engines are used throughout the film for what is supposed to be a propeller driven airplane." CORRECTION: Throughout the film the familiar rumbling sound of the aircraft's propellers is very clear. At no point in the film do the propellers sound like jet engines which would have a distinctively smooth and consistent whine.
This low budget film uses stock shots of the aircraft in flight. However, during the flight, the aircraft magically changes to various models of the Douglas DC series.
Meg Wyllie would later play the main alien in Gene Roddenberry's first "Star Trek" pilot, "The Cage", footage from which would be heavily reused in the 2-part episode, "The Menagerie."
As the airliner continues in altitude way above the usual airliner altitudes of those days the passengers and crew members would be unconscious. There is insufficient air at anything above 15-20,000 feet to have them remain conscious. As late as 100,000 ft the cockpit crew has gone on oxygen but everyone in back would be unconscious. Even the altimeter is wrong. When flying in the USA 'transition altitude' is around 18,000 ft-and the altimeter should be set to a standard altimeter of 29.92 inches of mercury. (That way all airliners are operating off a relative altimeter). The bottled oxygen within the airliner would be depleted in no time. More modern airliners (turbo-props) have their own oxygen systems within them to produce breathable air for the crews and passengers.