Three small airplanes crashed this long Labor Day weekend from North Carolina to Oregon, leaving 10 people dead and pressing questions about what happened in each case, a government official said Monday.

The deadliest crash occurred late Sunday afternoon, when a Cessna 310 went down in a remote part of Colorado near Telluride, the National Transportation Safety Board tweeted.

All five people aboard that aircraft died, according to NTSB spokesman Peter Knudsen.

How and why they died remained mysteries a day later, as Colorado National Guard and a search and rescue team converged on the site.

Three people were killed around noon Monday when a Beechcraft A36 crashed near a rock quarry about 6 miles from its intended destination in Greensboro, North Carolina, Knudsen said.

That plane’s pilot, who had taken off earlier from Sarasota, Florida, told air traffic controllers he was disoriented and trying to find his way to Greensboro’s airport. The NTSB spokesman said that controllers tried to steer the pilot to the airport, without success.

More than 2,000 miles away in Oregon, a small plane crashed near an airport in Creswell, Lake County Sheriff’s Office Lt. Chris Doyle said.

The two-seater crashed around 10 a.m. (1 p.m. ET) in a field near the airport in Creswell, which is about 12 miles south of Eugene. Authorities arrived to find the plane on fire and, eventually, that the two people inside — the 35-year-old pilot and his 83-year-old passenger — had died, according to Doyle.

Such fatal crashes are not rare.

For example, NTSB data indicates 115 people died in U.S. plane crashes between January 1 and May 31 of this year, including 29 in May alone. The vast majority of those deaths were on personal-use aircraft.