engineering, public affairs, hospitality, law, drug counseling, mail operations, security forces, and search and rescue specialties. Beyond combat flight crew personnel, other combat USAF AFSCs are Special Tactics Officer, Explosive Ordnance Disposal (EOD), Combat Rescue Officer, Pararescue, Security Forces, Combat Control, Combat Weather, Tactical Air Control Party, Special Operations Weather Technician, and AFOSI agents. Nearly all enlisted career fields are "entry level", meaning that the USAF provides all training. Some enlistees are able to choose a particular field, or at least a field before actually joining, while others are assigned an AFSC at Basic Military Training (BMT). After BMT, new enlisted airmen attend a technical training school where they learn their particular AFSC. Second Air Force, a part of Air Education and Training Command, is responsible for nearly all enlisted technical training. Training programs vary in length; for example, 3M0X1 (Services) has 31 days of tech school training, while 3E8X1 (Explosive Ordnance Disposal) is one year of training with a preliminary school and a main school consisting of over ten separate divisions, sometimes taking students close to two years to complete. Officer technical training conducted by Second Air Force can also vary by AFSC, while flight training for aeronautically-rated officers conducted by AETC's Nineteenth Air Force can last well in excess of one year. USAF rank is divided between enlisted airmen, non-commissioned officers, and commissioned officers, and ranges from the enlisted Airman Basic (E-1) to the commissioned officer rank of General (O-10), however in times of war officers may be appointed to the higher grade of General of the Air Force. Enlisted promotions are granted based on a combination of test scores, years of experience, and selection board approval while officer promotions are based on time-in-grade and a promotion selection board. Promotions among enlisted personnel and non-commissioned officers are generally designated by increasing numbers of insignia chevrons. Commissioned officer rank is designated by bars, oak leaves, a silver eagle, and anywhere from one to five stars. General of the Air Force Henry "Hap" Arnold is the only individual in the history of the US Air Force to attain the rank of five-star general. 70% of the Air Force is White, 15% Black and 4.8% Asian. The average age is 35 and 21% female. Commissioned officers The commissioned officer ranks of the USAF are divided into three categories: company grade officers, field grade officers, and general officers. Company grade officers are