Finishing second to Salt Lake for arrivals was Phoenix at 83.79 percent, followed by Seattle at 83.41 percent and Minneapolis-St. Paul at 83.18 percent.
In departures, Portland finished second at 86.16 percent, followed by Seattle at 85.59 percent and Minneapolis-St. Paul at 83.95 percent.
Chicago Midway had the nation's worst performance for departures, with only 66.6 percent on time followed by Chicago O'Hare at 70.37 percent, Denver at 72.51 percent and Newark Liberty at 72.65 percent.
Newark had the nation's worst arrival performance, with 70.36 percent of flights on time. Following it were New York LaGuardia at 72.17 percent, San Francisco at 72.66 percent and Chicago O'Hare at 73.52 percent.
Utah's top-in-the-nation performance last year was merely sort of average for it essentially matching its 10-year averages. Over the past decade, Utah's average ranking was 1.6 in the nation for departures and 1.8 for arrivals.
Airport spokeswoman Barbara Gann said the rankings are a mixture of good luck and hard work. Weather, efficiency by airlines and everyone cooperating to coordinate efforts all played a role.
"Typically the No. 1 factor contributing to on-time performance is weather. And we've been extraordinarily lucky this winter with very little impact to our operations especially in comparison to the rest of the country," which has had a tough year for weather-caused delays and cancellations, Gann said.
Also, she noted that Delta Air Lines which operates three of every four flights out of Salt Lake City with a major hub operation "is invested in connecting that traffic efficiently."
For example, she said Delta has its own ground-control tower. "That much of the traffic gets handed off to a separate tower," which tends to help smooth traffic.
Gann said that the "other seven airlines and the airport itself also work very closely together. We have a good team, and we coordinate carefully" to keep traffic moving.