The sole Do 18 converted with BMW 132 radial engines, probably seen on Lake Constance from where it first flew in this new Do 18L form on 21 November 1939. From January 1940 it underwent military testing at Travemünde coded CO-JF. The regular Do 18 suffered from its weak Jumo diesel engines but the more powerful radial in the pusher position gave cooling problems.

The Do 18 was designed as a transatlantic mailplane and, although 170 examples were built, it was unsuccessful as a military aircraft, underpowered by Jumo diesel engines, cramped and not all that seaworthy apparently. D-ANHR made a record flight of 8435 km (5241 miles) from the catapult ship Westfalen off the English coast to Brazil on 27-29 March 1938; it did not reach the intended destination, Rio de Janeiro. Afterwards it was tested with BMW 132 radials, becoming the sole Do 18L. Photo from: Nationaal Archief (Netherlands)