14% faster optimum cruise speed, and a 32% lower fuel burn for the S550. Sierra was announcing a IFR/VFR range for the re-engined Super II; or a IFR/VFR range for the re-engined Super S-II. By June 2012, Sierra Industries had re-engined 59 various Citations with FJ44s, among avionics retrofit and airframe modifications. Variants (Model 550), stretched development of the Model 500 with increased wingspan, fuel capacity and gross weight, 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. Citation II/SP (Model 551), single-pilot version of Model 550 with reduced gross weight. (Model S550), development of Model 550 introduced in 1984 featuring a supercritical wing with swept wing roots, increased fuel capacity, and various minor improvements. Initially replaced the II in production. T-47A (Model 552), U.S. Navy radar systems trainer version of S/II with a shortened wingspan, strengthened windshields, cockpit roof windows, more powerful JT15D-5 engines and military equipment. Citation Bravo (Model 550 Bravo), updated S/II with new PW530A engines, landing gear and Primus 1000 avionics.<ref name="aero-techbravo">[http://www.aerospace-technology.com/projects/cessna_bravo/ "Cessna Citation Bravo Light Business Jet Cessna Citation Bravo Light Business Jet, USA", Aerospace-Technology.com]</ref> The last Citation Bravo rolled off the production line in late 2006, ending a nearly 10-year production run of 337 aircraft. Operators Military operators Civilian operators Tyrol Air Ambulance Airline operator The Citation was also operated by at least one airline in scheduled passenger service being Enterprise Airlines in the U.S. from the late 1980s to 1990. Accidents and incidents On September 4, 2022, a Cessna 551 heading from Jerez, Spain did not land at its intended destination, Cologne, Germany, but instead kept flying across Germany and the Baltic Sea where it eventually ran out of fuel and crashed in the sea off Ventspils, Latvia. The pilot had reported problems with air conditioning and pressurization early in the flight but later stopped responding to communications. A possible cause of the crash is that loss of cabin pressure rendered everyone on board unconscious. Specifications (Cessna S550 Citation S/II) See also References Hoyle, Craig. "World Air Forces Directory". Flight International, Vol. 182, No. 5370, 11–17 December 2012. pp. 40–64. . Hoyle, Craig. "World Air Forces Directory". Flight International, Vol. 188, No. 5517, 8–14 December 2015. pp. 26–53. . Hoyle, Craig, Farfad, Antoine. "World Air Forces Directory". Flight International, Vol. 196, No. 5715, 10–16