Northrop Delta
- a single-engine, fixed gear transport aircraft developed in parallel with the Northrop Gamma
- wider fuselage, pilot's cabin moved to the nose
- just after production began, the government banned airlines from carrying passengers at night or over rough terrain with single-engine aircraft, hence the small success
Version overview:
Delta 1A - 8-passenger transport aircraft, Wright SR-1820-F3 engine, used by TWA as a mail plane, destroyed in a crash in less than a year
Delta 1B - similar transport aircraft with Pratt & Whitney Hornet T2D-1 engine, owned by Aerovías Centrales SA, also destroyed
Delta 1C - fast transport aircraft with Pratt & Whitney Hornet T1D-1 engine, deployed by AB Aerotransport between Paris and Stockholm; possibly later used by the Spanish Republicans or the Swedish Air Force for target towing
Delta 1EDelta 1E - a mail aircraft with a two-seat cabin at the trailing edge level like the Gamma, Hornet T2D-1 engine; flew with AB Aerotransport for less than a month, then crashed
Delta 1DDelta 1D - six-passenger saloon aircraft, SR-1820-F3 engine; modified rudder and cockpit glazing, higher back; first user Richfield Oil Corp. on the register in the 1970s
Delta 1D-1- transport aircraft, final cockpit design, SR-1820-F3 engine; purchased by Republicans through middlemen, captured by Nationalists aboard SS Mar Cantábrico and used by Gruppo 43; last recorded partially disassembled in 1939
Delta 1D-2Delta 1D-2 - similar to the D-1, eventually purchased by the Republicans and smuggled through France; flown first by LAPE airlines, then in Air Force colors; briefly used by the Nationalists in Grupo L-12 after the surrender
Delta 1D-3Delta 1D-3 - Hornet S4D-1 engine and then Hornet S9E, privately owned; destroyed in hangar fire 1939
Delta 1D-4 - SR-1820-F3 engine, purchased by Republicans through middlemen, captured by Nationalists aboard SS Mar Cantábrico and used by Gruppo 43, later Grupo L-12
Delta 1D-5Delta 1D-5 - saloon aircraft with SR-1820-F2 engine, used by Lincoln Ellsworth in Antarctica in 1939 and later purchased by the Australian government; destroyed 1943
Delta 1D-6Delta 1D-6 - SR-1820-F3 engine, owned by Pulitzer among others; purchased by the US Corps of Engineers in 1942 for transport during pipeline construction in Canada
Delta 1D-7Delta 1D-7 - ordered by the US Coast Guard under the designation Northrop RT-1, SR-1820-F2 engine; first a passenger plane for Treasury Secretary Henry Morgenthau, then as a staff plane; sold and repaired after crash, fate unknown
Delta 1D-8Delta 1D-8 - model aircraft for the Canadian Department of Defense, SR-1820-F52 engine, built by Canadian Vickers
Delta Mk.IDelta Mk.I - Canadian photo reconnaissance and transport variant, SR-1820-F52 engine, reinforced floor and cargo door, up to three crew, three Fairchild A3 cameras in fuselage, option of wheel, skid or float landing gear; 2 units, Delta 1D-8 modified to this standard
Delta Mk.IA - modified Mk.I with additional windows
Delta Mk.IIDelta Mk.II - similar to the Delta IA with the ability to carry a machine gun in a semi-covered gunnery loop on the back and bombs under the wing and fuselage; 9 pieces
Delta Mk.III - due to aerodynamic changes caused by the gunnery range, completely new tail surfaces; 1 conversion and 8 production