It was used right up until 1945.
This from Wikipedia:
Swedish count Eric von Rosen gave the Finnish White government its second aircraft, a Thulin Typ D. Its pilot, Lieutenant Nils Kindberg, flew the aircraft to Vaasa on 6 March 1918, carrying von Rosen as a passenger. As this gift ran counter to the will of the Swedish government, and no flight permit had been given, it resulted in Kindberg receiving a 100 kronor fine for leaving the country without permission. This aircraft is considered by some to be the first aircraft of the Finnish Air Force, since the Finnish Air Force did not officially exist during the Civil War, and it was only the Red side who flew a few aircraft with the help of some Russian pilots. The von Rosen aircraft was given the designation F.1. The air force was officially called the "aviation force" during its first years. The Finnish Air Force is one of the oldest air forces of the world – the RAF was founded as the first independent branch on 1 April 1918 and the Swedish Flygvapnet in 1925.
Von Rosen had painted his personal good luck charm on the Thulin Typ D aircraft. This charm – a blue swastika, the ancient symbol of the sun and good luck – was adopted as the insignia of the Finnish Air Force. The white circular background was created when the Finns tried to paint over the advertisement from the Thulin air academy. The swastika was officially taken into use after an order by Mannerheim on 18 March 1918. The FAF had to change the insignia after 1945, due to an Allied Control Commission decree, where the swastika had to be abandoned due to its association with Nazism.
Wyrd bið ful āræd.
"Coffee. The finest organic suspension ever devised. I beat the Borg with it."
- Capt. Kathryn Janeway