The PWS-54 was a Polish single-engine passenger and mail plane for three passengers; one alone was built in 1932 in the PWS factory.
The Zeppelin-Lindau Rs.II was a biplane flying boat, designed by Claudius Dornier as a follow-on to his Zeppelin-Lindau Rs.I and built during 1914–1915 on the German side of Lake Constance. Initially this aircraft was powered by three engines mounted inside the hull driving three pusher propellers via gearboxes and shafts. The later version was powered by four engines in two push-pull nacelles mounted between the wings.
The Zeppelin-Lindau Rs.III was a large four-engined monoplane flying boat designed by Claudius Dornier and built during 1917 on the German side of Lake Constance at the Zeppelin-Lindau works.
The Bréguet Leviathan was a family of large all-metal biplane aircraft built in France in the early 1920s. The Bréguet XX and XXI were notable for being powered by Bréguet-Bugatti multiple engines, in two forms. The Bréguet XXI was powered by individual Bréguet-Bugatti U.16 engines initially and Lorraine-Dietrich 8b engines in tandem later. The Bréguet XXII had accommodation for about twenty passengers and was destroyed during a 1923 transport aircraft competition. Development of all three aircraft types was halted largely due to technical issues with power-plants and aircraft structure.
The Potez XVIII was a French airliner from the early 1920s, a three-engine biplane carrying up to twelve passengers.
The Potez 38 was a French single engine, eight or nine seat passenger aircraft flown in 1930. Only one was built.
The Caudron C.91 was a French single engine biplane with an enclosed passenger cabin seating four. It first flew in 1923.
The Caudron C.74 was a ten-seat, four engine passenger biplane built in France in 1922. It showed promise but the sole prototype crashed fatally in a competition and no more were completed.
The Caudron C.39 was a French three-engined biplane with a cabin for six passengers when the aircraft was equipped as a landplane or four passengers when on floats. It was flown with some success in competitions in 1920 and 1921.
The Caudron C.33 "Landaulet Monsieur-Madame" was a French twin engined biplane with four seats, two in open cockpits and two in an enclosed cabin.
The Caudron C.25 was a large, three-engined, biplane airliner, designed and built in France soon after the end of World War I. Its enclosed cabin could accommodate up to eighteen passengers.
The Villiers 31 or Villiers 310 was a French eight passenger airliner of advanced construction. Owing to Villiers' financial failure, it was not developed.
The Caproni Ca.95 was a large, three engine, long range, heavy bomber prototype built in Italy in 1929. It could carry a 1,600 kg (3,500 lb) bomb load and had three defensive gun positions. Only one was built.
The Dornier Do S was a 22-passenger flying boat airliner flown in Germany in 1930.
The Aviaméta 92 was a French, all-metal, five seat monoplane built in the late 1920s. Three different engines were fitted, and one example flew the first non-stop Paris-Algiers flight in preparation for an abandoned trans-Atlantic attempt.
The LFG V 3 Susanna was a three seat, high wing monoplane flying boat with a single, pusher configuration engine mounted above the wing. A later variant, the LFG V 3a Susanne, was a bigger, more powerful four-seater. Only one of each was built.
The 1929 Curtiss Model 53 Condor, also known as the Curtiss Model 53 Condor 18 or the Curtiss CO Condor, was a civil passenger version of the Model 52 Condor bomber. A twin-engined biplane, it carried 18 passengers.
The McMullen Mac Airliner was a late 1920s American light airliner powered by a Liberty L-12 V-12 engine of World War I origin. The sole prototype was destroyed in a hangar fire.
The Zenith Z-6 is a single engine biplane U.S. airliner built in the late 1920s. Its cabin, in the fuselage immediately behind its radial engine, holds five or six passengers depending on engine power. It is flown from an open cockpit further aft. Nine were completed and one has been restored to flight.
The Fukunaga Tenryu 10 was the largest Japanese civil passenger aircraft when it first flew in 1922. Its passenger cabin seated four.
