Complex sentence: The 290 JCSS is associated with the U.S. Transportation Command's (USTRANSCOM) Joint Enabling Capabilities Command (JECC), the Joint Communications Support Element (JCSE), and is operationally-gained by Air Mobility Command (AMC).
Split into simpler sentences: The 290 JCSS is associated with the U.S. Transportation Command's Joint Enabling Capabilities Command (JECC) and the Joint Communications Support Element (JCSE). As a USAF organization, the 290 JCSS is operationally-gained by the Air Mobility Command (AMC).