How bad was the heat in Salt Lake City on Sunday? So bad that a plane set to land at Salt Lake City International Airport had to be diverted because of the record-breaking temperature, according to one passenger.

Brenna Huckaby, a Paralympic snowboarder who trained in Utah, posted on Threads that the Salt Lake City-bound plane she was on Sunday had to be diverted to Twin Falls, Idaho.

“The airplane I’m on can’t land until it’s 106 degrees out (currently 109),” Huckaby wrote. “That’s wild.”

The reason it’s harder to take off and land when temperatures are hotter, said Rick Stehmeier, a retired pilot and the airport’s assistant director of operations, is that “hot air is thin air.”

When the air passing through a plane’s engines is hotter, Stehmeier said, “you make less thrust, so less power.” Also, “there’s less air going over the wings, so you get less lift.”

Airports that experience higher temperatures more often than Salt Lake City, like Phoenix or Las Vegas, can keep operating up to around 115 degrees because they are at lower elevations.

But because of its altitude, Salt Lake City has thinner air already, even before it gets hot, he said, so a 109-degree high can be enough to change flight plans.

Huckaby did not identify the airline in her post, but an airport spokesperson said it’s believed the plane was flown by Utah-based SkyWest Airlines.

A SkyWest spokesperson said in a statement Monday afternoon that the airline “operated a full schedule in Salt Lake City on July 12 with 100% completion.” However, a small number of Delta Connection flights, operated by SkyWest, were delayed or diverted because of the heat, the spokesperson said, adding that the airline worked “to minimize disruption for travelers.”

The National Weather Service recorded a high temperature Sunday of 109 degrees in Salt Lake City — the hottest temperature the capital city has hit since records were first kept in 1874. The previous record was 107 degrees, the weather service said, which has been reached five times — in 1960, 2002, 2021 and twice in 2022.

An extreme heat warning for portions of central and northern Utah remains in place through Tuesday at 6 a.m., the weather service reported.

A longer runway at Salt Lake City’s airport could help keep planes flying in hotter temperatures, said Brady Fredrickson, the airport’s director of planning. The airport is in the early stages of seeking an extension of its main runway, from 12,002 feet to 14,520 feet.

Airport officials have presented what’s called a “justification study” to the Federal Aviation Administration, making the case that the runway should be lengthened. If the FAA approves, and an environmental plan is OK’d, the airport aims to start construction in 2030, with a completion date in fall 2033 — enough time to have the runway ready for the 2034 Winter Olympics.