The FF9 Kaje was a Norwegian built aircraft. It was designed and built by the Norwegian Army Air Service's aircraft manufacturer Kjeller Flyfabrikk.
The work towards the Kaje started in 1921. It was built in three series: the Kaje I of which ten were built in 1921 and 1922, the Kaje II of which four were built in 1925 and five Kaje III in 1926. The models were slightly changed in the wing profile, wing span and rudder surfaces based on experiences made on the previous model.
The Kaje was a well built aircraft with a good engine, but it had bad spin characteristics.
The model was primarily used as a training plane and for reconnaissance, but could also carry arms and was tested with radio equipment.
The plane was in use until the early 1930s.