A physician assistant may use the post-nominal initials "PA", "PA-C", "APA-C", "RPA" or "RPA-C", where the "-C" indicates "Certified" and the "R" indicates "Registered". The "R" designation is unique to a few states, mainly in the Northeast. APA stands for aeromedical physician assistant and indicates that a physician assistant successfully completed the US Army Flight Surgeon Primary Course. During training, PA students are designated PA-S. The use of "PA-C" is limited only to those PAs currently certified and in compliance with the regulations of the national certifying organization, the National Commission on Certification of Physician Assistants and who have passed the PANCE.