[3] On the part of the Royal Norwegian Air Service, the requirements were for a reconnaissance aircraft with a range of 1,500 km (930 mi), a top speed of no less than 320 km/h (200 mph) and to carry a 900 kg (2,000 lb) torpedo or the equivalent in bombs.

[3] On 30 December 1939, Norway sent a purchasing commission to the United States, consisting of a Royal Norwegian Navy Air Service contingent headed by Cmdr.

[3] After visits to many of the aviation companies in February 1940, Østby determined that only one manufacturer had both a design and available production capacity, Northrop Aircraft Incorporated.

Due to the use of the more powerful Cyclone engine, all performance estimates were exceeded and flight characteristics including maneuverability were considered "excellent".

Arrangements were made later in 1941 for the advanced flight training of Norwegian pilots to be carried out in RAF and RCAF schools on types that better fitted the transition to combat flying.

[4] The N-3PBs sent to Iceland were all shipped across the Atlantic in crates on board the Norwegian steamer Fjordheim, the voyage from New York to Reykjavik taking 13 days to complete.

Part of the reason for deploying the N-3PBs to Iceland was to avoid having the unusual aircraft operating over the United Kingdom, with the involved risk of friendly fire incidents.

[4][23] On a number of occasions in 1942, the N-3PBs clashed with Focke-Wulf Fw 200 long-range reconnaissance bombers and Blohm & Voss BV 138 flying boats,[24] being credited with at least one damaged.

[26][N 2] To publicize the N-3PB operations, the British Air Ministry circulated a report that two Norwegian-flown aircraft had been involved in the attack on the German battleship Bismarck on 21–22 May 1941 but this was a lie.

[32] Throughout the transition to other types, the squadron's C Flight maintained an "all-Northrop" unit, predominately involved in secondary roles including army cooperation, transport, air-sea rescue, ice reconnaissance and air ambulance.

Although the eight attacks they carried out on U-boats proved inconclusive, N-3PB escort patrols and antisubmarine sweeps were an important part of the Allied effort in keeping the North Atlantic sea lanes open.

[32] After the end of the type's combat service in Iceland, the Norwegian naval authorities considered basing two N-3PBs on Svalbard, an Arctic archipelago previously known as Spitzbergen.

[32] After a search through records, Ragnar R. Ragnarsson, then vice president of the Icelandic Aviation Historical Society pinpointed the crash site of N-3PB (c/n 320 ["U"]).

Due to bad weather over Iceland's east coast, the N-3PB flown by Lt. W.W. Bulukin, operating from Búðareyri and transiting to Reykjavik, made a forced landing on 21 April 1943.

[38] The complex restoration required the construction of replacement parts primarily by templating many damaged or corroded original aircraft components in order to create a complete airframe.

[40] On 27 August 2002, ICGV Baldur, while on a hydrographic surveying mission, discovered a relatively intact wreckage of a Northrop N-3PB lying upside down at the depth of around 11 m (36 ft) in Skerjafjörður, close to Reykjavík.

[41] A diving ban was imposed in a 20-meter radius of the wreckage, as it was unknown if the plane was carrying any bombs and, with the cockpit being closed, the likelihood of it being a watery grave.