AB Aerotransport purchased a second Delta, but this was a dedicated mailplane which more closely resembled the Gamma, with a slim fuselage carrying its cargo in a compartment ahead of the cockpit.

[2] One aircraft, the last Delta built by Northrop, was supplied as a part assembled pattern to Canadian Vickers, first flying on 16 August 1936 and being delivered to the RCAF on 1 September that year.

[8] The Northrop Delta was the first completely all-metal, stressed-skin aircraft built in Canada, however it was closely preceded by the Fairchild Super 71, whose stressed skin construction was limited to the fuselage and not the flying surfaces.

The Deltas, which were capable of being operated from wheeled, ski or float undercarriages, proved capable survey aircraft, well suited to operations in the north of Canada, but in August 1939, when the outbreak of the Second World War loomed, Canada found itself short of coastal patrol aircraft, and the Deltas were diverted to this role, being fitted with floats and carrying out long anti-submarine missions.

The Deltas were less successful as patrol floatplanes, as they were damaged by ocean swell and by salt water corrosion, and they were forced to revert to landplane use after two months.