Air Canada will move all of its 15 Embraer 175s to one of its regional partners in the first half of 2013 as part of an ongoing shift in the composition of its mainline fleet, but many questions about its fleet remain unanswered.

Partner Sky Regional will take delivery of the Embraer aircraft between February and June 2013, Air Canada says in a statement. Sky Regional will operate the aircraft on short-haul regional routes under the Air Canada Express brand.

The move is consistent with plans that Air Canada announced earlier this summer. President and CEO Calin Rovinescu said the airline’s 45 Embraer 190s and 15 Embraer 175s could become a fleet restructuring casualty.

Plans for the 45 Embraer 190 regional jets remain unclear at this time, an Air Canada spokesman tells Aviation Week.

The shift comes as Air Canada is set to add two Boeing 777-300ERs–part of five firm orders for 777s–to its mainline fleet between June and September 2013.

The restructuring also will enable Air Canada to release aircraft from its existing fleet to the low-cost carrier it plans to launch next year. The airline says details about the low-cost unit are forthcoming.

Air Canada previously said it might assign as many as 30 Airbus narrowbodies and 20 Boeing 767s already in its fleet to the new operation, which will target high-volume leisure markets normally associated with low-fare operations. In August, Rovinescu announced the launch of an internal review on how to proceed with a narrowbody replacement program to make Air Canada’s fleet more efficient.

The airline has begun recruiting pilots and flight attendants for the subsidiary.