During World War II, the US Air Force, the USAAF (United States Army Air Force), was not an independent type of armed force and was formally under the command of the army. Thanks to their excellent industrial base and efficient organization, they became the most powerful military aviation in the world during World War II. It is also worth remembering that the USAAF grew tremendously in terms of the number of personnel - in 1939 they numbered about 25,000 people, but at its peak, i.e. in the summer of 1944 - as many as 2,400,000 people! So in five years they have grown almost 100 times! In this number, approx. 300 thousand. were officers, while about 2.1 million were privates and non-commissioned officers, mainly from ground service. Despite such enormous growth, the USAAF implemented effective training systems and methods, which made the overwhelming part of the above-mentioned personnel perform their tasks efficiently. It can also be mentioned that all types of technical and mechanical facilities were used on a large scale in the work of ground handling, which shortened the number of hours needed to bring a given machine to take-off and flight. It is worth remembering that the number of US overseas air bases also increased dramatically, in December 1941 there were 19, and in May 1945 - as many as 130!