Southwest Airlines is phasing out its Boeing 737 Classic aircraft by about 2017 and is finding ways to use engine inventory from that fleet to decrease its maintenance costs.

Mandy Gower, Southwest Airlines’ powerplant supply chain manager, told Aviation Week that the airline employs MTU Canada and BP Aerospace in Irvine, Calif., to tear down its CFMI CFM56-3s that power the Classics. The airline just took the next step and selected Avioserv San Diego to consign the material. Avioserv, a company that specializes in the supply and sale of serviceable engines, will be Southwest’s sole consignment partner to feed used serviceable material back to the airline to decrease CFM56-3 engine overhaul costs. Several parts on the -3, which power Southwest’s 737-300/-400/-500 aircraft, are interchangeable with the CFMI CFM56-7, the engine on the 737-700. Avioserv also will market the excess engine inventory.