Four FF.33Es and four FF.33Ls stationed since 1916 at the German Naval Air Station Peynerdjik near Varna on the Black Sea were transferred in June 1918 to the Bulgarian Navy. They were scrapped in 1920 in accordance with the clauses of the Peace Treaty.
Finnish Air Force purchased two FF.33Es from Germany in February 1918. The first one arrived on 20 April 1918 to Vaasa and the other one in the summer of 1918. The aircraft wore the German designation numbers 1999 and 1998, which were changed into the FAF designation numbers F16 and F24 (later S58/18 and S73/18). Another FF.33E was purchased from the Germans in Estonia on 26 November 1918. The type was in FAF service between 1918–1923.
Wikimedia Commons has media related to Friedrichshafen FF.33.
^Y.Milanov: "The aviation in Bulgaria in the wars from 1912 to 1945, Vol.I". Sveti Gueorgi Pobedonosetz, Sofia, 1995 (in Bulgarian)
^Andrzej Morgała (1985), Samoloty w polskim lotnictwie morskim (Polish naval aviation aircraft), Warsaw: WKiŁ, ISBN 83-206-0478-8, p. 10-12
^Timo Heinonen (1992). Thulinista Hornetiin - 75 vuotta Suomen ilmavoimien lentokoneita (in Finnish). Tikkakoski: Keski-Suomen ilmailumuseo. ISBN 951-95688-2-4.
^Kober, Theodor von; Borzutzki, Siegfried. Flugzeugbau Friedrichshafen GmbH : Diplom-Ingenieur Theodor Kober (in German) (1. Aufl ed.). Burbach. pp. 106–107. ISBN 978-3927513600.
Anderson, Lennart (November–December 2019). "La renaissance de l'aviation militair bulgare dans les années vingt" [The Rebirth of Bulgarian Military Aviation in the Twenties]. Avions (in French) (232): 52–66. ISSN 1243-8650.
Cortet, Pierre (December 2001). "Rétros du Mois" [Retros of the Month]. Avions: Toute l'Aéronautique et son histoire (in French) (105): 7. ISSN 1243-8650.
Klaauw, Bart van der (March–April 1999). "Unexpected Windfalls: Accidentally or Deliberately, More than 100 Aircraft 'arrived' in Dutch Territory During the Great War". Air Enthusiast (80): 54–59. ISSN 0143-5450.
Nelcarz, Bartolomiej & Peczkowski, Robert (2001). White Eagles: The Aircraft, Men and Operations of the Polish Air Force 1918–1939. Ottringham, UK: Hikoki Publications. ISBN 1-902109-73-2.