LaTisha Wilkinson spoke to her father for over an hour on the phone on Friday, and she hasn't spoken with either of her parents since.

The missing couple, LaVerne and Van Pettigen, had planned an afternoon snow machine ride that day, but after missing an appointment on Sunday and a flight on Monday, family members are concerned that something went wrong.

"They're experienced riders," Wilkinson said. "They know the trails. They've had a place in Big Lake for around 10 years."

According to Wilkinson, she texted her father on Saturday and then her mother on Sunday, but got no response.

The Pettigen's neighbors checked their condo and found the couple's wallet, purse and other personal items. While the couple's snow machines were missing, both cars were accounted for and covered in snow.

According to Wilkinson, her mother left a voice message at 10:53 a.m. Sunday morning.

The last cell signal pinged by searchers occurred at around 10:30 a.m. on Tuesday.

Alaska State Troopers and the Alaska Rescue Coordination Center are currently searching the area where the couple is believed to have been riding.

Big Lake Trails Inc., a non-profit trail advocacy group, is planning a volunteer search Wednesday morning. In a Facebook post Tuesday night, organizers asked for any volunteers with snow machines to meet at 10 a.m. on the land bridge between Mud Lake and Big Lake.