The CASA C-101 Aviojet is a low-wing single engine jet-powered advanced trainer and light attack aircraft. It remains in service in the Spanish Air Force and some other countries; it is also flown by the Patrulla Aguila aerobatics team.It was designed to replace the already outdated Hispano Saeta. Spanish aircraft maker CASA began work on the C-101 in 1975. Germany's MBB and the USA's Northrop helped with the development, and the first four prototypes flew in June 1977.