Search efforts continue for a B.C. man and an Alberta woman, missing in B.C.'s interior since Thursday when their plane failed to arrive in Kamloops.

Alex Simons, 21, of Kamloops, and Sydney Robillard, 24, of Lethbridge, Alta., were travelling from Lethbridge to Kamloops in a small Piper Warrior aircraft piloted by Simons on Thursday.

They stopped to refuel in Cranbrook midday, but never made it to Kamloops.

The Joint Rescue Coordination Centre (JRCC) has established a command centre in Kelowna to coordinate the search.

More than 15 aircraft are searching the area, including three military planes, two military helicopters and more than 10 civilian volunteers.

Air task force commander Lt. Col. Bryn Elliott said low-lying clouds were making the search difficult due to the many high mountain ranges between Cranbrook and Kamloops.

"When you have to search peaks that are up at 9,000, 10,000 feet, you know, a 6,000-foot cloud layer makes it very difficult for us," Elliott said.

The JRCC says Simons and Robillard were travelling in a Piper Warrior aircraft, like the one shown in this photo. (Ahunt/Wikimedia Commons)

Elliott said the size of the search area is also proving to be a challenge; as of Saturday evening, crews had only thoroughly searched 15 per cent of the 350-kilometre stretch between Cranbrook and Kamloops.

Elliott said there was bad weather in the area on Thursday when the plane went missing, but crews have no firm leads as to what actions Simons might have taken in response.

"Part of the search is a bit of investigative work, a bit of detective work," Elliott said "We're looking at all options to see what he might have done if he had encountered bad weather."

Though it's been more than 48 hours since the plane was reported missing, crews remain hopeful.

"We're still very much in search and rescue mode," Elliott said.