CSS has shared a first look at its two upcoming 737 Classic freighters, the 737-300SF and 737-400SF, and the previews come with an interesting detail: the two cargo jets are modeled on two different real-world conversions, so they won’t be identical.
The freighters complete the Classic family, following the passenger -300 and -400 that released earlier this month and the -500 before them. They’ve been on the roadmap since November’s pricing overhaul. There’s no release date yet, but CSS has put out enough to get a sense of where the cargo versions are heading.
Two conversions, two different jets
Boeing never sold the 737 Classic as a factory freighter, so every cargo Classic flying today is a third-party conversion. CSS notes that the work has been handled over the years by companies such as IAI of Israel, whose version carries the 737-300BDSF designation, and the Florida-based PEMCO and AEI, whose conversions wear the -300SF and -400SF labels. Operators often ended up with quite different airframes even within the same fleet, since the original build options, the year of manufacture, and the conversion vendor all varied.
Rather than apply one generic template to both, CSS says it has modeled the PEMCO conversion for the 737-300SF and the AEI conversion for the 737-400SF. According to the developer, that choice carries through to cargo door placement, the galleys, and small differences in cockpit equipment, so the two freighters should feel distinct if you fly both.
A livery pack made with JSWorks
CSS has also confirmed a collaboration with JordxnE and AJP Creations from JSWorks on a base livery pack, which the team says covers both current and former 737 Classic freighter operators.
The -400SF list draws heavily on real cargo names: DHL via Cargoair, West Atlantic, Kalitta Charters II, Swiftair, Aloha Air Cargo, FedEx through ASL Airlines, Mercado Libre through Aeronaves TSM, and several more. The -300SF roster is just as varied, with SF Airlines, Bluebird Cargo, Buffalo Airways, Royal Mail through Titan Airways, Qantas Freight through Express Freighters Australia, and Aerosucre among the names on offer. If you fly virtual cargo routes or run a freight-focused VA, there’s a good spread of paint to pick from here.
Pricing, and what’s still to come
The pricing follows the structure CSS set out earlier. Owners of the full 737 Classic Family package will get both freighters at no extra cost. If you only bought a passenger variant on its own, the matching freighter will run you an additional $10 each.
CSS hasn’t put a release date on the freighters yet. The team says more previews are on the way, including the interiors and a closer look at the -300SF, so this is more like a first reveal. Of course, we’ll cover the freighters properly once they become available.



















