Mechon Carriers appear during the events of Xenoblade Chronicles and are mainly used to dispatch other Mechon troops. While they occasionally appear in cutscenes and the background, they are never encountered during gameplay.
Mechon are an effective means of moving large numbers of Mechon by air. Multiple models can be transported, including the M31, M63, M69, M72 and even the M82. Larger models such as faced Mechon have their own air-capable propulsion systems, and so don't need to be transported using a Mechon Carrier.
Mechon Carriers have a domed top, with a single engine at the back emitting a blue light. The individual Mechon are housed on the underside of the vehicle and transported in a dormant state. When it comes time to deploy the Mechon, they are activated (identified by a red light coming on) and can be released from the vehicle as individual units. As Mechon are able to fall a long way with little to no damage, the Carrier does not need to be able to land or even fly low in order to deploy its full payload.