United Airlines spokeswoman Megan McCarthy says the man collapsed Sunday evening on the jetway leading to the terminal.
She says paramedics were called immediately.
But accounts of the event differ. Army Reserve medic and passenger Jared Noall told KSL) he and two others performed CPR on the man in the aisle of the plane until paramedics arrived.
The man, who the station says appeared to be in his 30s, was later pronounced dead.
Salt Lake City airport spokeswoman Barbara Gann declined to release the person's age, gender or name. She says airport police are looking into the situation.
