The Air Transport Command was an organisation that exist between 1942 and 1948. Its personnel and equipment were contracted from civilian airlines and put under control of the US Army Air Force (USAAF).
Its purpose was to fly aircrafts to were they were needed (repair bases or to the front) and to ferry equipment oversea. Until 1941 this had been done by the US Army Air Corps/USAAF but the increasing demand in performing these duties as well as the transport of troops, training and combat operations lead to the creation of the ATC that would concentrate solely on ferrying duties.
It should be noted that a number of pilots serving within the ATC were women, part of the Women Airforce Service Pilots (WASP).
The various uniforms worn were the same type as USAAF personnel but with their own insignias.
Rank was indicated by metallic bars on the shoulders straps and an equal number of rings on the cuffs of jackets.
ATC specific wings were also worn. Note that role and ranks went together so that there were no "3 bars" flight mechanic nor "1 bar" pilots.