sentences:  Because of unreliable engines and quite big fuel consumption resulting from their high power output, most PZL.26s were not used in Polish sports aviation much after the Challenge.SP-PZL, -PZM, -PZN and - PZP were removed from the registry on July 1, 1936.The SP-PZO was used until the war in 1939 by the Pomeranian Aeroclub in Toruń.