These long range boats were frequently equipped with Focke-Achgelis Fa 330 rotor kite towed rotary-wing aircraft. Types IXA and IXB had an additional periscope in the control room, which was removed in Type IXC and afterward. Anti-aircraft armament differed throughout the war.

Secondary armament was provided by one 10.5 cm (4.1 in) deck gun with 180 rounds. Some of the IXC boats were fitted for mine operations as mine-layers they could carry 44 TMA or 66 TMB mines. The total of 22 torpedoes allowed U-boat commanders to follow a convoy and strike night after night. They carried six reloads internally and had five external torpedo containers (three at the stern and two at the bow) which stored ten additional torpedoes. Type IXs had six torpedo tubes four at the bow and two at the stern. It was derived from the Type IA, and appeared in various sub-types. Type IX boats were briefly used for patrols off the eastern United States in an attempt to disrupt the stream of troops and supplies bound for Europe. The Type IX U-boat was designed by Nazi Germany's Kriegsmarine in 19 as a large ocean-going submarine for sustained operations far from the home support facilities. 6 × Daimler-Benz MB501 20 cylinder Diesel marine engines with total power of 9,000 horsepower (9,100 PS 6,700 kW) (IX-D/42 Variant).French Navy (post war U-123 as Blaison and U-510 as Bouan).

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