A full two-thirds of the movie is actually set in Utah (or, technically, in the air above Utah). A 747 airplane is struck by a small single-person airplane whose pilot had a heart attack. The characters who must land the plane must communicate with Hill Air Force Base and the Salt Lake Int'l Airport, and you hear "Salt Lake City" spoken at least 40 times in the movie.
And, yes, there are Mormon jokes. A pilot (maybe Heston, I'll have to check) tells mission control, "Tell Brigham Young we're on our way."
A young boy, after hearing that the plane is being diverted to Salt Lake, excitedly asks his mother, "Can we visit the Mormon temple?"
A festively boozing Jack Klugman ("The Odd Couple") says sardonically that he visited Salt Lake City once... "It was closed."
Some familiar faces include Jerry Stiller (Jerry Seinfeld's father from "Seinfeld"), Karen Black in the lead female role, Charlton Heston as lead actor, Gloria Swanson in a supporting role as screen legend Gloria Swanson (she plays herself). And, of course, singer Helen Reddy as the guitar-playing nun, "Sister Ruth." Other stars include Myrna Loy, Linda Blair, Erik Estrada and Efrem Zimbalist Jr. There is also an overtly Jewish blonde stewardess and Hare Kishna (ISKON) passengers, which was fun.
The movie even has Latter-day Saint actor Ken Sansom in supporting role.
Part of the movie was filmed on location at the Salt Lake International Airport. There also lots of scenes of the plane flying over Utah, and if you look carefully you might be able to spot your own house. No CGI. It's all real footage.
One interesting and commendable aspect of the movie is the fact that there was not a single villain in the whole movie. Unlike the original "Airport" movie, which had a suicide-bomber-for-insurance-money subplot, "Airport 1975" revolved around the crisis that arises from a rather simple and believable accident. The movie may seem deathly slow to attention deficit kids of today, but I rather enjoyed it.
Ultimately all the crew and passengers (except a few who died on initial impact with the other plane) are saved by going to Salt Lake City. "Airport 1975" is one of the rare Hollywood movies that implies that safety, truth and happiness can be found in the Church.