their aircraft which may bear only coincidental resemblance (if that) to the official popular name, although some pilot nicknames are similar or even derived from the official popular name (such as "Bug" and "Super Bug" for the F/A-18 Hornet and F/A-18E/F Super Hornet). There are seven potential components of a system's MDS designation as well as three potential components which are not included in the MDS. Aircraft designation Status prefix Status prefix is an optional prefix not often used for vehicles in regular service. If used, it is the first letter in the MDS. Authorized current status prefixes are: e Digitally developed. Vehicles that are developed in a digital environment. G Grounded. Applied to aircraft which are permanently grounded, most often used for ground training of crews and support. This is only applied as a permanent designation. Use is rare. J Temporary Special Test. Applied to craft involved with special testing of temporarily installed equipment. The J Prefix is used for aircraft that can be reasonably returned to their original configuration following tests. An example is aircraft used as testbeds for new electronics, but which will or may not retain that equipment after tests are complete. N Permanent Special Test. Applied to craft involved with special testing on a permanent basis, with modifications to their configuration that make return to original configuration impractical. Many military aircraft transferred to NASA for aeronautical research carry this designation. X Experimental. Applied to craft which are not yet accepted for service, or to prototypes for which standard configuration has not been finalized. Most prototypes of the past carried this prefix, but it should not be confused with craft given an X basic mission symbol. The X status prefix is for designs for other missions, but at an experimental stage of the design process. An example shown earlier is the XWC-130J. Y Prototype. Originally applied to demonstration craft where configuration had been determined, but from the 1970s on applied to all prototypes of aircraft intended for production. An example would be the prototype YF-22 Z Planning. Applied to designs in the planning/pre-development phase. Modified mission symbols Many craft have been designed for more specific missions than their basic mission symbol would indicate, and many design series have been designed for different missions than the original design, and may or may not still maintain capability for the original mission. The modified mission symbol provides the services