Aircrafts greatly used V12 engines in the past. After the First World War, V12 engines became very common in the new bombers and fighters of that time. Companies like Sunbeam and Renault were among the manufacturers of them.
V12 engines became very popular during the Second World War. Bombers and fighters made use of V12s like Rolls-Royce Merlin, Griffon, Klimov VK-107, Allison V-1710 and Junkers-Jumo. At the starting of war these engines produced a power of about 750 KW and at the full advanced stage they produced more than 1100 KW.
German DB 605D engines produced about 1,500 kW through water injection. Daimler-Benz, Argus, and Junkers-Jumo were basically inverted. They had the benefits of enhanced visibility and low center of gravity. There also came an engine called BMW VI V12 which was the upright one.
The V12 engine has a narrow and long configuration which is a must in the field of aerodynamics. After the second world war the use of V12 engines declined drastically in the aircrafts due to the coming up of turboprop and turbojet engines.