Broadly similar in design and layout to the Do 18, the Do 24 had three radial engines mounted separately on the wing leading-edge, and twin fins and rudders. At the prompting of the Netherland's Marine Luchtvaartdienst, in 1935 Claudlus Dornier set about developing a replacement for the WAL seaplanes which was already thirteen years old and totally obsolete.
Working to Dutch specifications Dornier installed, Wright R-1820 Cyclones in the Do 24 V3 and V4, temporarily shelving the Jumo 205-powered V1 and V2. D-ADLP, the V4, was used for open sea trials at Bodensee and proved to be a. typically tough Dornier airplane. Plans were made to build 60 Do 24Ks under license in the Netherlands, but following diversion of part of the funding to buy additional Martin 139s (export versions of the B-10 medium bomber) this order was cut to 48 planes. When Germany invaded Holland in 1940, 25 Do 24Ks were captured in various stages of completion and were used for air-sea rescue work in the North Sea and English Channel. The seaplane was evaluated at Erporoblingsstelle-See Travemunde and was judged to be so suitable for this mission that production was resumed in Holland, BMW-Bramo Fafnir radials replacing the American Wrights with the result that the machine was redesignated Do 24T, additional aircraft being built in occupied France as well.
The first of three prototypes to fly, on July 3, 1937, was the Do 24 V3 (D-AYWI), pow-ered by 875-hp Wright Cyclone R-1820-F52 engines. This aircraft, plus the V4 and ten similarly-powered Do 24K-1s were delivered to the Dutch navy, and apart from the Jumo 205C-engined V1 and V2 were the only German-built examples.
Production continued with 28 Dutch-built Do 24K-2s, powered by 1000-hp R-1820-G 102 engines, and carrying revised armament and up to 1250-kg (110-lb) bombs. Twenty-five of these were delivered to the Dutch East Indies. The other three, and eight partially-built K-2s, were captured in 1940 and completed to Luftwaffe standards as Do 24N-1 air/sea rescue aircraft. From this the major ASR/transport version, the Do 24T-1, was developed with 1000-hp Bramo 323R-2 engines. Armament consisted of a 20-mm (0.79-in) Hispano cannon in a dorsal turret and single 7.9-mm (0.311-in) machine-guns in the bow and stern positions. One hundred and eighty of these were built (110 in Holland and 70 by CAMS in France).
Of the 294 Do 24s built (including prototypes) only 37 saw service with the Dutch East Indies navy, for whom it was originally designed in 1935.
By contrast, some 222 were employed by the Luftwaffe.
Forty-nine Dutch-built Do 24T-2s were sold to Spain, and in 1944 Spain also purchased 12 generally similar Dutch-built Do 24T-3s, powered by three 1,000 hp BMW engines. These were used to provide an air-sea rescue service in the Mediterannean, the Spanish machines picking up downed crews of any nationality. Only 48 of the French-built T-Is reached the Luftwaffe, the remainder being 'liberated' and used as transports by Flottille 917 Tr of the French Aetonavale starting in December 1944 with the first two.
The Dutch East Indies Dorniers operated for some time against Japanese shipping in the southwest Pacific; those of the Luftwaffe saw action in the Baltic, English Channel, Mediterranean and the Black Sea.