Excerpt from Wikipedia:

Air Transport Command (ATC) was a United States Air Force unit that was created during World War II as the strategic airlift component of the United States Army Air Forces.

It had two main missions, the first being the delivery of supplies and equipment between the United States and the overseas combat theaters; the second was the ferrying of aircraft from the manufacturing plants in the United States to where they were needed for training or for operational use in combat. ATC also operated a worldwide air transportation system for military personnel.

Inactivated on 1 June 1948, Air Transport Command was the precursor to what became the Military Air Transport Service in 1948 and was redesignated Military Airlift Command (MAC) in 1966. It was consolidated with MAC in 1982, providing a continuous history of long range airlift through 1992 when the mission was transferred to today’s Air Mobility Command.

During training, among Tom’s possible ultimate assignments was flying cargo planes, or delivering new aircraft from the factory to combat theaters for the Air Transport Command.