Willis Lease Finance Corporation, along with its subsidiaries, is a lessor and servicer of commercial aircraft and aircraft engines. The Company operates through two segments: Leasing and Related Operations, and Spare Parts Sales. The Leasing and Related Operations segment involves acquiring and leasing, primarily pursuant to operating leases, commercial aircraft, aircraft engines and other aircraft equipment and the selective purchase and resale of commercial aircraft engines and other aircraft equipment and other related businesses. The Spare Parts Sales segment involves the purchase and resale of after-market engine parts, whole engines, engine modules and portable aircraft components. The Spare Parts Sales segment also enables the Company to provide end-of-life solutions for surplus aircraft and engines, as well as manage the full lifecycle of its lease assets. Its subsidiaries include WEST Engine Funding LLC, Willis Aeronautical Services, Inc., and Willis Asset Management Limited.