Model Variants (Including Prototypes)
Mk I - Initial Production Model; powered by Hercules XI radial engines; 756 such models produced.
Mk II - Prototype Variant fitted with Wright Cyclone powerplants; never placed into production.
Mk III - Fitted with Hercules XVI powerplants; 875 produced as such; became main bomber production variant; first Stirling design fitted with twin-gun dorsal turret assembly.
Mk IV - Transport and Glider Tug Model; sans nose and dorsal gun emplacements; 577 such models produced.
Mk V - Transport Model Variant; 160 such models produced.