The Beech Baron's ID number is N9750Y, as you can clearly see every time they show the plane in flight, but every time Scott (the pilot) communicates with Air Traffic Control, the plane is addressed as Baron 232Z.
After the collision, Captain Stacy turns the auto-pilot "A" switch on manual, leaving the "B" off. But in following shots, the two buttons switch positions and Nancy turns on and off the "B" switch.
As Flight 409 approaches Salt Lake City, it is dawn. However, some interior shots showing total darkness outside are followed by exterior shots of the plane flying in sunlight.
During the evacuation of the 747 after landing, Beverly Garland (who played the Baron's pilot's wife) can be seen evacuating from coach.
At the end of the film, the shot of the hole in the plane shows touched-up gray paint and no hole in the cockpit fuselage.
There is a major concern that the little girl who needs the kidney transplant will die because she will be off her dialysis machine for too long. A normal dialysis schedule is four hours, three times per week. If the girl was removed from a dialysis machine a few hours before boarding the plane, she would have two to three days before her next required treatment with no risk, even if she had total kidney failure.
When the 747 is coming in for the landing at Salt Lake City, the passengers are not in the "brace" crash position. As there was damage to the plane, an engine out and problems with braking control, prudence would have dictated that the crew would have had the passengers in the "brace" crash position.
When the air traffic controller asks Nancy to look at "the third fuel used gauge" on the engineer's panel, she reports "22500 pounds". However, this doesn't indicate a fuel leak, since it's from the fuel USED gauge. The number on the gauge to the right, 24530, is what indicates a fuel leak, as more fuel has been used from that tank than the others.
It is mentioned that 120 lives are at stake on the plane. A 747 seats over 400, so there should be a lot of empty seats on the plane.
Referring to the autopilot, Al asks Nancy, "Is it in manual"? Nancy replies, "It's on manual; it's on", but the switch is clearly in the "OFF" position.
Sister Ruth is shown wearing a wedding ring. The Catholic Church regards nuns as "Brides of Christ" and as such wear wedding rings as a symbol of that union.
When the two passengers look out the right side of the 747, they notice fuel leaking from the wing. However, when it reaches the rear flaps, some of the fuel simply drips vertically down off the rear edge of the wing, indicating no rearward airflow to the underside of the wing, revealing the 747 is motionless.
The passengers on board watch the pilot being winched from the jet helicopter into the 747. However, this would be impossible from the angle in which we see the helicopter flying and the position of the passengers seated on board.
Even though the 747 is going at least 140 mph (the helicopter's maximum speed), the cabin does not show signs of the 140 mph wind gusts that would be blowing. There are even scenes where Charlton Heston's and Karen Black's hair isn't blowing wildly.
Alan Murdoch and Joe Patroni leave the air traffic control center to board the helicopter; in the next shot, the plane goes over a mountaintop. Following this, when passengers are shown aboard Flight 409 looking directly forward, crew members can be heard in the background giving instructions to the actors. A crew member quite clearly says, "Yeah."
As the 747 approaches the end of the runway at Salt Lake, it swerves to the left. Inside the airplane, all the passenger are thrown to the left, toward the inside of the turn.
Shortly after the 747 takes off, Mrs. Patroni hands her son a book and says, "Study this chapter and don't move until I get back." The book she hands the boy is the 1963 edition of "Hoyle's Rules of Games", an unlikely source of study material for a pre-teen child.
When Gary says "Whatever happened to womanhood?" his lips do not move.
When the pilot is being winched from the jet helicopter into the 747, inside the cockpit, the roar of the helicopter engine or blades is not heard.
Alan (Charlton Heston) is obviously dubbed over in the first scene. His lips do not match all of his words.
The plane takes off from Washington Dulles Airport in complete darkness, in the early hours of the morning. It heads west to Los Angeles, however on the exterior shots of the plane flying west, dawn is seen rising in the west and not the east.
The wife of the Baron pilot is seen at the Salt Lake City airport with a TV reporter. However, according the the plot, she lived in Boise, Idaho, which is more than 300 miles away. If the local airport was closed due to bad weather, there is no way she would be able to make it to Salt Lake in such a short amount of time.
The 747 landing shots alternate between Salt Lake City and another airport. In one shot, a huge piece of equipment to the right of the runway is seen, and in another shot, it's gone, etc. After the landing, the evacuation takes place at a completely different airport.
Mr. Kelly tells Janice Abbott's doctor that he has gotten the ambulance special clearance through Gate 4. That means that the ambulance would access the airport field about two miles south of the airport terminal directly from Route 28 - a road that runs north/south parallel to the airport. In a later scene, the ambulance is stuck in a traffic jam turning south off of East Service Road about a mile north of the Dulles Airport main terminal. A vehicle entering the airport through Gate 4 would have absolutely no business being anywhere near East Service Road.
When Salt Lake loses communication for the second time, neither Murdoch nor Patroni knows this as they are in the helicopter. So when Nancy is performing a climb, Patroni states that she is flying it herself, which although accurate, both Patroni and Murdoch would assume that ground control is talking her through it.
In Airport (1970), Joe Patroni mentioned that his wife was named Marie and he had five children, but in this film, his wife is renamed Helen and he has just one son. In The Concorde... Airport '79 (1979), Patroni mentions his wife has died in a car accident and he only has one son.