Air Transport Services Group (ATSG) is the world's largest lessor of mid-sized freighter aircraft, focused primarily on converted Boeing 767s serving e-commerce and express delivery networks. ATSG's core business starts with acquiring used passenger aircraft — typically 15-20 years old — and converting them into freighters, then leasing them under long-term contracts (typically 5-10 years) to cargo operators. Amazon and DHL are the two largest customers, together accounting for roughly 47% of 2024 revenues. ATSG operates through two segments: CAM (Cargo Aircraft Management), the leasing business, and ACMI Services, which provides airline operations through three subsidiaries — ABX Air, ATI, and Omni Air International. These airlines fly cargo for Amazon and DHL and passenger charters for the U.S. DoD. ATSG's "Lease Plus" model bundles aircraft leasing with ACMI/CMI operations, where customers supply aircraft and pay ATSG to operate them, plus ancillary maintenance and ground services. This integration is ATSG's key differentiator from pure-play lessors. The business is capital-intensive, requiring heavy upfront investment in aircraft acquisition and conversion, but generates predictable contracted cash flows once aircraft are deployed. ATSG is also expanding into A330 and A321 freighter conversions to diversify beyond the 767. ATSG was taken private via a merger agreement signed in November 2024, with closing anticipated in the first half of 2025.