The primary freighter conversion programs for the Boeing 777-300ER are led by Israel Aerospace Industries (IAI), Mammoth Freighters, and Kansas Modification Center (KMC), but none have yet received Supplemental Type Certificates (STC). IAI is anticipated to secure the first STC by May 2025. IAI’s conversion program has over 60 orders, while Mammoth and KMC are also making progress, with Mammoth nearing completion of prototypes and KMC focused on its certification process. Meanwhile, Boeing has ceased production of the passenger variant but continues with the freighter version, maintaining strong demand in the market.

Source: https://www.stattimes.com/air-cargo/iai-mammoth-and-kmc-push-ahead-with-boeing-777-300er-freighters-1354827