When was the last time you enjoyed an open seat next to you on a flight to or from Salt Lake City International Airport?

“Not too often, unless you are flying late at night or some off-peak time,” David Dague, executive vice president of InterVistas, told the airport advisory board on Wednesday.

In fact, the average flight in or out of Salt Lake City is now 83.3 percent full, and such “flight loads” here are consistently higher than the industry average.

When flights are that full, “that is our alarm to think about how we can talk to these carriers about expansion” for more flights serving the city, or perhaps using larger aircraft, said Dague, a consultant who helps with the airport’s marketing and future planning.

He said flights by Delta into its Salt Lake City hub are now 84.1 percent full on average. Percentages among other airlines here include: United, 86.1 percent; Frontier, 87.1 percent; JetBlue, 85.2 percent; KLM, 83.4 percent; American, 82.8 percent; Southwest, 81.3 percent; Alaska and Air Canada, 71.7 percent each.

With such heavily booked flights, Dague said, airlines often “are not able to carry every passenger that wants to get on that flight.” One example: Dague said he tried to fly Delta from Boston to Salt Lake City this week, but the flight was full.

“I’m sure Delta would have liked to take my money if they could — but the seats weren’t there,” he said.

Even late-night flights — when seats usually are more open — are still often packed.

Such full flights are attracting more service to Salt Lake City, he said. The airport expects to expand service by 5 percent this year — which makes the airport the ninth fastest growing among the nation’s large airports, and it is now the nation’s 24th largest.

Dague said that has helped create a convenient network of service from Salt Lake City, which now has 342 peak day departures to 97 non-stop destinations.

He notes that 47 of the top 50 destinations or origin points for Salt Lake travelers now have non-stop service from Salt Lake.

However, over the past five years, Salt Lake City’s domestic fares have been on average 5 percent higher than the industry — but Dague said that margin has been closing.