Delta 1A
Prototype.
Powered by 710 hp (530 kW) Wright SR-1820-F3 Cyclone radial engine.
One built.

Delta 1B
Passenger airliner for Pan-Am.
 Powered by 660 hp (490 kW) Pratt & Whitney Hornet.
One built.

Delta 1C
Passenger airliner for AN Aerotransport.
Powered by 700 hp (520 kW) Hornet.

Delta 1D
Executive aircraft, powered by Cyclone or Hornet engines.
Eight built, including one Northrop RT-1, powered by 735 hp (548 kW) Cyclone for United States Coast Guard.

Delta 1E
Airmail carrier for AB Aerotransport.
One built.
Powered by 660 hp (490 kW) Hornet.

Delta I
Survey aircraft for RCAF.
Powered by 775 hp (578 kW) SR-1820-F52 Cyclone.
Three built, including pattern aircraft and two license built.
Based on the 1D-8.

Delta IA
Partial modification to Mk.
II standards, with bomb racks fitted.

Delta II
Revised version with provision for armament, including bombs, a dorsal turret mounting a .30 in Browning machine gun (later removed) and two wing mounted machine guns.
 Nine built.

Delta III
Unofficial designation for Mk.
II fitted with enlarged tail surfaces to counter tail buffeting from turret.
Eight built.

RT-1
United States Coast Guard designation for its sole Delta 1D-7, which was named "Golden Goose".
Delta 1A
Prototype. Powered by 710 hp (530 kW) Wright SR-1820-F3 Cyclone radial engine. One built.
Delta 1B
Passenger airliner for Pan-Am.  Powered by 660 hp (490 kW) Pratt & Whitney Hornet. One built.
Delta 1C
Passenger airliner for AN Aerotransport. Powered by 700 hp (520 kW) Hornet.
Delta 1D
Executive aircraft, powered by Cyclone or Hornet engines. Eight built, including one Northrop RT-1, powered by 735 hp (548 kW) Cyclone for United States Coast Guard.
Delta 1E
Airmail carrier for AB Aerotransport. One built. Powered by 660 hp (490 kW) Hornet.
Delta I
Survey aircraft for RCAF. Powered by 775 hp (578 kW) SR-1820-F52 Cyclone. Three built, including pattern aircraft and two license built. Based on the 1D-8.
Delta IA
Partial modification to Mk.II standards, with bomb racks fitted.
Delta II
Revised version with provision for armament, including bombs, a dorsal turret mounting a .30 in Browning machine gun (later removed) and two wing mounted machine guns.  Nine built.
Delta III
Unofficial designation for Mk.II fitted with enlarged tail surfaces to counter tail buffeting from turret. Eight built.
RT-1
United States Coast Guard designation for its sole Delta 1D-7, which was named "Golden Goose".
Northrop Delta