Smith said heavy snow that has been falling all day Monday and low clouds have twice grounded planes and Idaho Army Air National Guard helicopters brought in to help search by air. Crews began focusing on the ridge top just east of the landing strip based on cell phone signals, Smith said.
"We have no idea what the status of things is right now," he said. "They could have landed safely somewhere and just can't communicate."
Signals from the plane's built-in emergency locator transmitter, designed to go off in crashes, have not yet been detected, he said.
One of the passengers is Jonathan Norton, a senior at BYU-Idaho, said Norton's uncle, Alan Dayton, of Salt Lake City. Norton grew up in Salt Lake City and is a senior accounting major. Norton was traveling with his fiance and classmate, Amber Smith, and her family following Thanksgiving vacation, Dayton said. Norton, Smith and her family traveled from San Jose to Baker City and were continuing to Butte to drop off Smith's brother and sister-in-law, Dayton said. Smith's father then planned to take his daughter and Norton back to Rexburg.
The couple planned to get married Jan. 4; Norton was "at the top of his class" and has several job offers waiting for him, Dayton said.
"The family is extremely worried," Dayton said. "There's a feeling of helplessness."
Authorities would not confirm the identities of the plane's occupants on Monday night. The plane's registered owner is Dale Smith, of San Jose, Calif., according to Federal Aviation Administration records. Smith obtained his pilot's license in 2005 and had a second-class medical certification, allowing him to operate commercial aircraft.
A telephone message left by the Associated Press on Monday at Smith's home was not immediately returned.