Typically in movies, most of the passengers on an airplane are played by extras. A few will be cast or costumed to be a "type", and some may have lines and get paid more, but most are just poorly-paid seat-fillers who are cast to look like unexceptional travelers.
In the 2012 movie Flight, Denzel Washington famously turns the plane upside down to avoid crashing. During that amazing sequence, all the passengers are shown hanging upside down in the inverted cabin. My question is whether all of those people were stunt actors (which would have significantly increased the cost of the flying sequence since there were so many of them), or were they untrained extras (who would have been paid a lot less, but could have gotten hurt because of the unusual conditions).
It's worth noting that extras in movies "fill seats" on roller coasters and other wild amusement park rides. It seems as though the inverted airplane set in Flight could have been just as safe as a roller coaster.