Production ceased in 1985.[3] Oldest flying Citation I Citation I/SP (Model 501) single-pilot operations[4] Citation II (Model 550) a larger stretched development of the Model 500 first produced in 1978. Initially replaced by the S/II in production, but was brought back and produced side-by-side with the S/II until the Bravo was introduced.[5][6] T-47 (Model 552) is the military designation of the Citation II. The U.S. Navy procured 15 T-47A aircraft as radar system trainers, and the DoD purchased five OT-47B models for drug interdiction reconnaissance.[7] Citation II/SP (Model 551) single-pilot operations[5][8] Citation S/II (Model S550) incorporated a number of improvements, especially an improved wing.