Fokker F.IX

The Fokker F.IX was an airliner developed in the Netherlands in the late 1920s, intended to provide KLM with an aircraft suitable for regular services to the Dutch East Indies. When the onset of the Great Depression forced the postponement of those plans, the market for this aircraft disappeared as well, although it did see military service in Czechoslovakia as a bomber.

Design and development
The F.IX was a three-engine, high-wing monoplane of conventional configuration, equipped with tailskid undercarriage. The wings were made of wood, and the fuselage was welded steel tube with a fabric covering. When presented at the 1930 Paris Air Show, it won the Grand Prix de Comfort et d'Elegance d'Avions de Transport - the "beauty prize" as voted by the public.

Czech aircraft manufacturer Avia purchased a licence to produce the type in order to create a bomber for the Czechoslovakian Air Force, when it was decided that the Fokker F.VII that Avia was already producing under licence was too small for this role. By 1932, 12 were in service as the F.39. Yugoslavia also purchased two aircraft, as well as a licence to produce the type domestically, although this did not eventuate. The F.39s differed from their civil counterparts not only in the addition of bomb racks, but also in a defensive machine gun being fitted to either a ventral "step" or a turret. Avia also built two examples as airliners for Czechoslovakian Airlines as the F.IX D (Dopravni - "transport"). One of these survived into World War II, when it was impressed into Luftwaffe service (as TF+BO).

A further proposed military development by Avia, the two-engine F.139, never left the drawing board.

Operational history
Even though KLM directors had been talking in terms of ten or more aircraft in 1929, the worsening economic climate resulted in only two being purchased. Due to the logistics implications of stocking spares for only two aircraft, these were confined to European routes and the two F.IXs only ever made one flight each to the Indies. One (registration PH-AFK) was written off in a crash on 4 August 1931, and the other (De Adelaar, PH-AGA) was retired in 1936 and was subsequently acquired by clandestine means to serve as a bomber in the Spanish Republican Air Force during the civil war.

Fokker

 * F-IX
 * Three-engined passenger airliner for KLM.

Avia

 * F.39: Three-engined bomber aircraft for the Czechoslovakian Air Force.
 * F.139: Proposed twin-engined version of the F.39. Not built.
 * F-IX D: Three-engined passenger airliner for Czechoslovakian Airlines.

Operators

 * Independent State of Croatia
 * Zrakoplovstvo Nezavisne Države Hrvatske
 * Czechoslovakian Airlines operated two aircraft.
 * Czechoslovakian Air Force
 * 🇩🇪 Germany
 * Luftwaffe operated one captured aircraft.
 * KLM operated two aircraft.
 * 🇪🇸 Spain
 * Spanish Republican Air Force
 * Kingdom of Yugoslavia
 * Yugoslav Royal Air Force
 * Kingdom of Yugoslavia
 * Yugoslav Royal Air Force

Accidents and incidents

 * On August 4, 1931 a KLM F.IX crashed on takeoff from Waalhaven Airport due to engine failure; all 15 passengers and crew survived, but the aircraft was written off.