Luke Bucklin was struggling to get his small airplane over Wyoming's tallest peaks in the moments before it crashed on October 25, according to a Federal Aviation Administration (FAA) recording obtained by The Associated Press (AP).

Just before the crash, which killed the Sierra Bravo Corporation leader and three of his sons, Bucklin told ground controllers that his four-seat single-engine Mooney 201 might not reach the 16,000-foot altitude assigned by an air traffic controller, the recording indicated. It was snowing heavily at the time.

“Descending rapidly,” Bucklin said on the recording.

“Reporting severe mountain waves,” he added about a minute later. “Probably going to (garble).”

That was the last audible transmission from Bucklin, according to the AP, which obtained the recording through a Freedom of Information Act request.

The National Transportation Safety Board (NTSB) hasn't disclosed the cause of the crash, but a preliminary report that it issued in November indicated that Bucklin's plane took off from Jackson Hole, Wyoming, just after 1 p.m. Mountain Daylight Time amid a snowstorm and was tracked by the FAA until about 1:36 p.m., at which time it was flying at 14,000 feet. At about 1:41 p.m., Bucklin radioed in, saying that he “was encountering a light chop and a trace of rime icing.” Rime icing-a granular deposit-is similar to what builds up in older models of freezers, and it can diminish a plane's lift and performance. At about 1:52 p.m., the plane was picked up by radar for the last time at an altitude of 13,300 feet.

After a week-long search, searchers found the plane on the evening of November 1 at 11,000 feet in the rugged mountains of western Wyoming on a slope about six miles southeast of Gannett Peak.

Wyoming's Fremont County Coroner Ed McAuslan said in November that all four of the Bucklin passengers-Luke, 40, and his sons, 14-year-old twins Nick and Nate, and 12-year-old Noah-died as the result of blunt force trauma they suffered in the crash.

The four Bucklins had been returning to Minneapolis from Wyoming after a wedding and vacation. Luke Bucklin's wife, Ginger Bucklin, and his 5-year-old son, Oliver, were also on the trip but took a commercial flight home on October 24.

Bucklin was president and cofounder of Bloomington-based Sierra Bravo Corporation, which in November changed its name to The Nerdery. It employs about 100 people and is among the state's largest Web development and design companies.