Willis Lease Finance is an independent lessor and servicer of commercial aircraft engines. The company leases spare engines to airlines and MROs worldwide, capitalizing on the fact that airlines need spare engines beyond those installed on aircraft, as engines cycle through mandatory maintenance regularly. Rather than owning spare engines outright, airlines increasingly lease them to offset the large capital cost of modern engines. Willis maintains a portfolio of roughly 363 engines and 20 aircraft leased to 69 customers across 37 countries. The engine portfolio focuses on widely-used engines from CFM International, GE Aerospace, Pratt & Whitney, and Rolls-Royce, powering Airbus, Boeing, Bombardier, and Embraer aircraft. Willis earns revenue primarily through fixed monthly lease payments and usage-based maintenance reserve fees. Willis also actively trades engines out of its portfolio, consistently realizing gains above book value. A differentiated product called ConstantThrust allows Willis to buy an airline's engine fleet and immediately replace any unserviceable engine from Willis' own inventory, effectively outsourcing engine availability management for the airline. Willis funds its portfolio with equity and debt, periodically refinancing into long-term fixed-rate Asset-Backed Securities. The company also manages engines for third-party investors, including fund partnerships with Liberty Mutual and Blackstone, earning fees without full balance sheet exposure. Willis operates two FAA-certified MRO facilities and is expanding its services footprint. The company's leasing segment accounts for roughly 95% of revenue, with the remainder from spare parts sales through subsidiary Willis Aero.